PORTABLE CONDENSATION-FREE TEMPERATURE-ADJUSTABLE RADIANT COOLING BOARD SYSTEM

Abstract

The present invention provides a portable condensation-free temperature-adjustable radiant cooling board system. The system includes a supporting panel, a movable stand holding the supporting panel and an angle-adjuster. The supporting panel includes at least one water pipe layer, at least one insulation layer on one side of the at least one water pipe layer, at least one high emissivity radiative layer on the other side of the at least one water pipe layer and at least one low humidity layer in front of the at least one high emissivity radiative layer. The invented PRCB has high flexibility in the creation and adjustment of microthermal environments for diverse personal thermal comfort requirements, thus broaden the applicability of PRCSs in hot and humid climates.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the priorities from the U.S. provisional patent application Ser. No. 63/488,524 filed Mar. 6, 2023, and the disclosure of which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention generally relates to a radiant cooling board. More specifically the present invention relates to a condensation-free radiant cooling board (PRCB).

BACKGROUND OF THE INVENTION

Buildings consume one-third of the total electricity energy generated by conventional fossil fuels and renewable energy systems, and half of that one-third is used to condition indoor spaces for thermal comfort. As predicted in previous research, air-conditioning demand is expected to increase by more than 4.5 times in developing countries. Space cooling, essential for maintaining thermal comfort within buildings in hot and humid climates, constitutes a significant source of greenhouse gas emissions. This emphasizes the urgent need to reduce energy consumption in this context.

A personalized radiant cooling system (PRCS) is a type of temperature-adjustable cooling system that has recently garnered significant attention due to its superior management of fan noise and cold draft issues compared to a personalized ventilation system (PVS). The PVS is “an individually controlled air distribution system aimed at improving the quality of inhaled air and the thermal comfort of each occupant”¹³. It creates a comfortable microthermal environment for occupants through enhancing Q_c by using a high airflow rate, i.e., a larger contribution from βT_a in Eq. (2)^14-16. As different body parts of human beings have different sensitivity to a cool environment, a PVS is always implemented to cool the head and upper body to improve the temperature sensation and the thermal comfort of a human body in a warm environment¹¹.

However, since a PVS should be placed close to a user, the cool air with a high velocity will always produce a cold-draft and noise. This unwanted local thermal discomfort could hardly be avoided when using PVSs, especially in hot and humid climates. The PRCS suffers from condensation and cooling power insufficiency when used in hot and humid climates. Increasing the radiant cooling temperature mitigates the risk of condensation but reduces cooling power, whereas decreasing the radiant cooling temperature enhances cooling power but enlarges the risk of condensation.

Furthermore, in existing designs of PRCS, the cooling capacity is very limited. This limitation arises from the necessity of maintaining the radiant cooling surface temperature at around 20° C. to prevent condensation, thereby restricting the applicability of PRCSs.

In light of these considerations, there is an urgent need to explore innovative solutions to enhance the effectiveness of PRCS in hot and humid climates, addressing the dual challenges of condensation risk and cooling power limitations.

SUMMARY OF THE INVENTION

The objective of the present invention is to provide a design for a condensation-free temperature-adjustable radiant cooling board that can be utilized to establish a comfortable microthermal environment for individuals in high ambient air temperatures (e.g., 28° C.-32° C. in a large office). The height/distance of the PRCB can also be adjusted according to users' physiological characteristics (e.g., body height), psychological needs (e.g., customization), and the limitations of environmental factors (e.g., workspace size). Thus, the invented portable condensation-free PRCB will be competitive in the market to meet diverse personal thermal preferences.

Moreover, the proposed technique can result in significant energy saving for buildings. For instance, this method can achieve an annual energy saving of over 16.9% compared to a conventional “one-fits-all” air-cooling system. The present invention, therefore, represents a significant stride towards more efficient, personalized, and environmentally conscious cooling solutions, with the potential to dramatically reduce energy consumption and mitigate the effects of global warming.

In a first aspect, the present invention provides a portable condensation-free temperature-adjustable radiant cooling board system. The system includes a supporting panel, a movable stand holding the supporting panel and an angle-adjuster for user-selected change of a facing angle (θ) of the supporting panel towards the user. The supporting panel includes at least one water pipe layer, at least one insulation layer on one side of the at least one water pipe layer, at least one high emissivity radiative layer on the other side of the at least one water pipe layer and at least one low humidity layer in front of the at least one high emissivity radiative layer.

The supporting panel has a multi-layer structure including at least one water pipe layer covered with at least one thermally-conductive conforming layer; at least one insulation layer on one side of the at least one water pipe layer; at least one high emissivity radiative layer on the other side of the at least one water pipe layer, the high-emissivity radiative layer creating a radiant cooling surface with an adjustable temperature range between 5° C. and 20° C.; and at least one low humidity layer in front of the at least one high emissivity radiative layer, sealed by an infrared-transparent membrane over a radiant cooling surface in conjunction with at least one side frame, with desiccant materials positioned on the at least one side frame to maintain dryness within the air-layer, the low humidity layer having a humidity of less than 35% such that the radiant cooling board system does not generate condensation.

In an embodiment, the water pipe layer includes supply fluid capillaries and return fluid capillaries.

In an embodiment, the high emissivity radiative layer is a thin metal layer coated with a high emissivity radiative paint. The thin metal layer has a thickness in a range of 0.08-0.10 mm. The high emissivity radiative layer comprises a graphene carbon nanotube coating with an emissivity of 0.95-0.98.

In an embodiment, the infrared transparent membrane has a thickness of 0.015-0.02 mm. The infrared transparent membrane has a transmittance rate of at least 80% for infrared waves within the wavelength range of 2.5-22 μm.

In an embodiment, the infrared transparent membrane is made from pure low-density polyethylene (LDPE).

In an embodiment, the low humidity layer has a thickness ranging from 5-10 cm.

In an embodiment, the facing angle (θ) is in a range of 60-90 degrees.

In an embodiment, the portable condensation-free temperature-adjustable radiant cooling board system has an inlet for receiving chilled water and an outlet for returning the water to a chiller.

A radiant cooling surface on the portable condensation-free temperature-adjustable radiant cooling board has a temperature ranging between 5° C. and 20° C. when utilizing the robust and lightweight supporting panel.

In another aspect, the present invention provides a method for accommodating diverse individual thermal comfort preferences in hot and humid climates, including installing said at least one portable condensation-free temperature-adjustable radiant cooling board system on each side of a user to create a microthermal environment. A distance between the portable condensation-free temperature-adjustable radiant cooling board system and the user is defined as “D”, and the D is in a range of 60-90 cm, and the supporting panel is mounted on a movable stand, and an angle-adjuster is used for user-selected change of a facing angle (θ) of the supporting panel towards the user.

In an embodiment, the facing angle (θ) is in a range of 60-90 degrees.

In an embodiment, a radiant cooling surface on the portable condensation-free temperature-adjustable radiant cooling board has a temperature ranging between 5° C. and 20° C. when utilizing the robust and lightweight supporting panel.

In an embodiment, the method further comprising introducing supply water and return water into the at least one portable condensation-free temperature-adjustable radiant cooling board system.

The advantages of this invention include: the newly developed PRCB boasts a substantial improvement in cooling capacity while mitigating condensation risks through the utilization of a radiant cooling temperature as low as 5° C. This innovative approach enables the provision of a comfortable thermal environment, even in the presence of elevated ambient temperatures, such as reaching up to 30° C. Additionally, a distinctive feature of the PRCB lies in its adaptable design. Users have the convenience of easily personalizing adjustments based on their comfort preferences. The radiant cooling temperature can be customized within the range of 5° C. to 20° C., while the facing angle is adjustable in the span of 60°-90°.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described in more details hereinafter with reference to the drawings, in which:

FIG. 1 depicts a schematic diagram of the portable condensation-free PRCB;

FIG. 2 depicts a schematic diagram of a facing angle between the PRCB and its user;

FIG. 3A depicts the schematic diagram of the low humidity layer sealed by a high IR transparent membrane. FIG. 3B depicts schematic diagram of the main layers of the robust and lightweight supporting panel;

FIG. 4 depicts the use of two PRCB to create temperature-adjustable microthermal environment;

FIG. 5 depicts the enhancement of radiative heat exchange between the human body and its surroundings to match human body's heat dissipation pattern;

FIG. 6 depicts the use of portable condensation-free temperature-adjustable radiant cooling technique in a large-scale indoor office for energy saving;

FIG. 7A depicts local mean radiant temperature establishment: radiant cooing surfaces↔occupant↔surrounding surfaces. FIG. 7B depicts local air temperature establishment through non-radiative heat exchange: radiant cooing surface↔membrane↔local air↔ambient air;

FIG. 8 depicts a measurement scheme for investigating the microthermal environment, ambient environment and the radiant cooling panel (RCP) pair, where the cooling supply water is provided by an air-cooled chiller;

FIG. 9A depicts the local air temperature generated from the PRCB pair with 1 m×0.7 m at T_c in a range of 4-22° C. under the ambient temperature of 31.3° C., 29.2° C. and 27.7° C. respectively. FIG. 9B depicts the local MRT. FIG. 9C depicts the local operative temperature T_op;

FIG. 10 depicts a lower test-point membrane temperature T_m (Error bars, standard deviation<±0.1° C., n=360);

FIG. 11A depicts an infrared camera image of a subject in the thermal survey. FIG. 11B depicts thermal sensation vote at different T_c when the ambient temperature was 28° C. and 30° C.;

FIG. 12A depicts the radiant cooling temperature fulfilling the requirement of (−0.5<TSV<0.5) when the RCP with different size was used for T_amb=28° C. FIG. 12B depicts the radiant cooling temperature fulfilling the requirement of (−0.5<TSV<0.5) when the RCP with different size was used for T_amb=30° C. (Error bars, maximum and minimum indication error, n=168);

FIG. 13A depicts thermal sensation votes at different T_op when the relative humidity was between 40%-60%. FIG. 13B depicts PMV values at different T_op when the relative humidity was between 40%-60%;

FIG. 14 depicts a calculation boundary schematic and office operating schedule;

FIG. 15A depicts the energy saving potential of the PRC system in a cooling season at T_amb=28° C. and TSV=0. FIG. 15B depicts the energy saving potential of the PRC system in a cooling season at T_amb=30° C. and TSV=0; and

FIG. 16A depicts the energy saving potential for different systems with different occupancy in a typical day. FIG. 16B depicts energy consumption for different systems with different occupancy in a typical day.

DETAILED DESCRIPTION

In the following description, the PRCB and/or adjustable method and the like are set forth as preferred examples. It will be apparent to those skilled in the art that modifications, including additions and/or substitutions may be made without departing from the scope and spirit of the invention. Specific details may be omitted so as not to obscure the invention; however, the disclosure is written to enable one skilled in the art to practice the teachings herein without undue experimentation.

Scientists and engineers have devoted much effort to understanding the mechanism to achieve thermal comfort and develop measures to improve the energy efficiency of indoor space conditioning³. It has been demonstrated that in a built indoor environment, human's metabolic body heat (Q_hm) is dissipated to the environment mainly through convection (Q_c), radiation (Q_r), and evaporation and respiration (Q_e), as represented by Eqn. (1)

$\begin{array}{cc}{Q}_{\mathrm{hm}}=Q_c+Q_r+Q_e& \left(1\right)\end{array}$

Controlling convection (Q_c) and radiation (Q_r), heat exchange with the environment, is the main technology for creating thermal comfort for human beings. Q_c is mainly determined by the temperature T_a and the velocity v_a of the air surrounding the human body, estimated by Q_c=h_a(T_hums−T_a), where T_hums is the equivalent surface temperature of human body, and h_a is an effective convective heat transfer coefficient, representing a nonlinear relationship with v_a⁵. Q_r is determined by a mean radiant temperature (MRT) of the thermal environment of an enclosure, where the human body is considered as the center of the enclosure, calculated by Q_r=h_r(T_hums−MRT), where h_r is the equivalent radiative heat transfer coefficient, highly depending on the cloth wear on the human body and the radiative properties of the surrounding surfaces, such as their emissivity and reflectivity of the surface materials.

The MRT in the built environment is defined as the uniform temperature of an imaginary enclosure, in which the radiant heat transfer from the human body is equivalent to the radiant heat transfer in the actual non-uniform enclosure⁷. Because T_hums (depending on human body temperature and the clothes he/she wears) is relatively uncontrollable, MRT and T_a becomes the two critical variables in creating comfortable thermal environments for occupants.

In built environment science, operative temperature (T_op) is always used to characterize thermal comfort, which is defined as a uniform temperature of an imaginary black enclosure, in which an occupant would exchange the same amount of sensitive heat by radiation plus convection as in the actual non-uniform environment. The operative temperature is calculated by⁷.

$\begin{array}{cc}{T}_{\mathrm{op}}=\alpha \mathrm{MRT}+\beta T_a& \left(2\right)\end{array}$

where α=h_r/(h_r+h_a) and β=h_a/(h_r+h_a) are weighting factors, indicating the contribution of MRT and T_a to the operative temperature and thus to Q_r and Q_c in Equation (1).

Variant techniques have been developed to regulate MRT and/or T_a. In cooling technology, these techniques are categorized into air-cooling and radiant cooling. The former achieves thermal comfort mainly through the regulation of T_a; while the latter mainly through the regulation of MRT. Both of them can be used to create a global thermally comfortable indoor environment, in the form of “one-fits-all” system, or a local thermally comfortable indoor environment, in the form of personalized comfort system (PCS)⁸.

Space cooling accounts for a substantial portion of energy consumption, significantly contributing to global warming. Conventional “one-fits-all” space cooling systems, which cool down entire spaces, inevitably lead to cooling waste because unoccupied areas, usually the major parts of large rooms, are also cooled. In contrast, a PCS has been considered as a better technique to save energy in conditioning a large-scale indoor space, especially when this space is partially occupied^9-10. This is because a PCS for cooling enables the use of higher ambient temperature (e.g., T_a=28° C.) than a “one-fits-all” system (e.g., T_a=24° C.), presenting a big step towards building conditioning with theoretical minimum thermal load⁴.

As reported, a PCS could increase the ambient temperature by 4.2° C. compared with a “one-fits-all” system under the same outdoor thermal conditions¹¹, which might lead to a huge energy saving as the increase of 1° C. could save energy by around 3%^12-13. Generally, PCSs for cooling is always realized using personalized ventilation systems (PVSs). However, since a PVS should be placed close to a user, the cool air with a high velocity will always produce a cold-draft and noise. This unwanted local thermal discomfort could hardly be avoided when using PVSs, especially in hot and humid climates.

Accordingly, the present invention provides a portable condensation-free temperature-adjustable radiant cooling board system. The system includes a supporting panel, a movable stand holding the supporting panel and an angle-adjuster for user-selected change of a facing angle (θ) of the supporting panel towards the user. The supporting panel includes at least one water pipe layer, at least one insulation layer on one side of the at least one water pipe layer, at least one high emissivity radiative layer on the other side of the at least one water pipe layer and at least one low humidity layer in front of the at least one high emissivity radiative layer.

In particular, the PRCB is installed on a movable stand with four wheels, allowing users to adjust the distance between the PRCB and themselves. Users could adjust the distance at a suitable value according to users' custom and work space. The present temperature-adjustable radiant cooling technique overcomes the limitations of PVSs, resolving a long-standing challenge in the field of indoor radiant cooling: the trade-off between preventing condensation and enhancing cooling power when radiant cooling is used in indoor spaces under hot and humid climates.

Different from existing PRCS designs, such as radiant cooling cubicles and the radiant cooling desks that do not address the condensation problem, or a radiant cooling board that integrates a drainage system into the board to collect water droplets when condensation occurs, the proposed PRCB can efficiently prevent condensation on the membrane even when the radiant cooling surface temperature is low (e.g., 5° C.).

Referring to FIG. 1, the assembled PRCB has a robust and lightweight supporting panel 100 affixed with a water pipe layer 2 on one side, and an insulation layer 1 on the opposite side. The water pipe layer 2 is covered with a thermally-conductive conforming layer such as a silicone grease conductive layer 4 to enhance the heat transfer between the fluid inside the capillaries and the radiant cooling surface and improve the uniformity of the temperature distribution on the radiant cooling surface. An IR transparent membrane 6 is used to seal one low humidity layer 7 over the radiant cooling surface with the side frames 5. Desiccant materials 9 are hung on the side frames 5 to maintain the air inside the air-layer at a low humidity level. The whole PRCB is installed on a movable stand equipped with four wheels, facilitating its mobility.

In one embodiment, the water pipe layer includes a set of supply fluid capillaries 11 and return fluid capillaries 12.

An angle/height adjuster 10 is used to change the facing angle (θ) of the board to users, as defined in right part of the FIG. 2. The facing angle (θ) is the angle formed between the center of the supporting panel 100 and the chest center of the user. The angle/height adjuster enables users to adjust the facing angle of the panel (to users), which produce different thermal sensation of different body parts of users for individual preferences.

The adjustable facing angle (θ) may cause changes in the thermal sensation of different body parts of users because of the change in the view factor for radiation. The angle/height adjuster 10 will further enhance the application flexibility of the PRCB.

It should be noted that the distance between the PRCB and users will affect the view factor as well. In principle, the shorter the distance is, the larger the view factor between the user and the PRCB is. Therefore, a short distance will enhance the heat exchange between users and the PRCB. However, the distance shall not be too short to affect users' work space in a large-scale office. Users could adjust the height and distance at a suitable value according to users' body height, custom, the limitation of work space, etc.

The thermally-conductive conforming layer may be a silicone grease conductive layer, which can enhance heat transfer between the fluid within the capillaries and the radiant cooling surface, thereby improving temperature uniformity across the radiant cooling surface.

In one embodiment, the thin metal layer coated with a high emissivity radiative paint may be graphene carbon nanotube coating with an emissivity of approximately 0.95.

In one embodiment, the IR transparent membrane may be pure LDPE membrane. The IR transparent membrane is characterized by high infrared transparency, ensuring that cooling power from the low-temperature radiant cooling surface is effectively applied to occupants. The IR transparent membrane has a transmittance rate of at least 80% for infrared waves within the wavelength range of 2.5-22 μm, allowing efficient passage of infrared radiation. This design enables the use of low radiant cooling temperatures (e.g., 5-15° C.) to enhance the cooling capacity without condensation. For instance, the IR transparent membrane has a transmittance rate of at least 85%, at least 90%, or at least 95%.

In one embodiment, the IR transparent membrane has a thickness of 0.015-0.02 mm.

Preferably, the IR transparent membrane has a thickness of 0.02 mm.

In one embodiment, the low humidity layer has a thickness around 5-10 cm. The dry air-layer provides a large thermal resistance for the conductive/convective heat transfer between the IR transparent membrane and the radiant cooling surface, which can help to maintain the IR transparent membrane at a high temperature (e.g., 20° C.) to prevent condensation even if the radiant cooling surface temperature is low (e.g., 5° C.).

In one embodiment, the facing angle is controllable within the range of 60°-90°, considering the stronger cooling requirements of the head and upper body parts for personal thermal comfort. The lower temperature of the upper body parts, especially the head, can contribute to better comfort and thermal sensation for the entire body. A facing angle of 60°-90° C. an better meet the cooling needs for each body part.

In one embodiment, the distance between the PRCB and users is defined as “D”, where the range of D is 60-90 cm.

In another aspect, the present invention also provides an efficient method for handling condensation problem and therefore enables a low radiant cooling temperatures (e.g., as low as 5° C.) for enhancing cooling capacity.

Due to the significant reduction of the space to be conditioned (compared with one-fits-all air conditioning), the PRC system may lead to significant energy saving. For example, the energy-saving potential exhibits a wide range, ranging from 10% to 90%. In a cooling season, the PRC system achieved 16.9% and 17.3% average energy-saving potential at TSV=0 under a T_amb=28° C. and T_amb=30° C., respectively, compared with an air-cooling system.

Through a comprehensive examination of the microthermal environment, thermal comfort, and energy performance of the PRCS, the feasibility of the proposed technique for application in hot and humid climates is demonstrated. For detailed information, please refer to the following examples.

EXAMPLE

Example 1—Assembly of Portable Condensation-Free Temperature-Adjustable Radiant Cooling Board

Referring to FIG. 3A, the radiant cooling surface was decoupled from the air-contact surface using a low humidity layer sealed by a high IR transparent membrane. The thermal resistance of the low humidity layer (to both conductive and convective heat transfer) with suitable thickness (>5.5 cm) can provide a significant temperature increase in the membrane referring to the radiant cooling surface temperature)^28-30, thus can efficiently avoid condensation even when a low radiant cooling temperature is used to enhance the cooling power^31,34. The strength of the radiative heat exchange between the occupants (e.g., 35° C.) and the radiant cooling surface (e.g., 5° C.) will not be much attenuated by the membrane when the membrane is highly infrared transparent and thus ensure the enhanced cooling power being effectively applied to occupants.

FIG. 3B showed the main structure of the supporting panel 100, including a low humidity layer 7, a high emissivity radiative layer 8, a water pipe layer 2 and an insulation layer 1. The high emissivity radiative layer was a cooling thin plate made of metal, ensuring even temperature distribution on the radiant cooling surface. The external surface of the cooling plate was used as a radiant cooling surface, coated with high emissivity materials (e.g., graphene-composite carbon nanotube with an emissivity of about 0.95) to enhance its emissivity power. In front of the cooling plate was the low humidity layer 7, which was scaled with a high IR transparent membrane. Behind the cooling thin plate was the water pipe layer 2 with water inlet and outlet interfaces to form a chilled water loop and cool down the plate layer. An insulation layer 1 was placed on the other side of the water pipe layer 2.

The supporting panel 100 was further installed on a movable stand to create a personalized radiant cooling board (PRCB), as depicted in FIG. 1. It is important to note that desiccant materials 9 were necessary to maintain the sealed air dry for an extended period.

The temperature of the radiant cooling surface on the condensation-free PRCB can range between 5° C. and 20° C. when utilizing the membrane-assisted radiant cooling panel. The inclusion of the 5° C. temperature is based on its significance as the typical chilled water supply temperature of chiller plants, enabling the direct use of chilled water without the need for retrofitting.

Example 2—Creating the Microthermal Environment to Accommodate Diverse Individual Thermal Comfort Preferences

To create a microthermal environment for an occupant, two PRCBs, or a PRCB pair, were installed on the right and left-hand side of the occupant, as shown in FIG. 4.

The radiant cooling surfaces of the PRCB pair have formed a personalized microthermal environment, inheriting the advantages of a conventional radiant cooling system (typically installed on the ceiling of indoor spaces as radiant cooling panels). These advantages included lower noise levels, reduced vertical temperature differences, lower draft risk, and so on^20-21.

Similar to PVSs, PRCSs were positioned in close proximity to users. However, unlike a PVS, a PRCS employed radiant cooling surfaces to provide a cooling sensation, primarily extracting heat from users by enhancing Q_r, i.e., relying on a larger contribution from αMRT in Eq. (2). This enhanced radiative heat exchange had the potential to improve the thermal sensation of occupants compared to a PVS. In a comfortable thermal environment, the ratio of radiation heat dissipation to total metabolic body heat Q_r could be 45-50%, as shown in FIG. 5.

FIG. 6 illustrated an application scenario of the proposed PRC systems, where a pair of PRCBs was installed for each workstation to establish a microthermal environment instead of cooling the entire office. Individual PRCB pairs could be easily switched on or off, similar to a desk lamp.

In the proposed radiant cooling technique, the microthermal environment was defined as the thermal conditions of the imaginary cuboid made by the PRCB pair, where the pair formed two opposite planes while the other four surfaces are virtual. The dimension of the four virtual surfaces depended on the distance between the PRCB pair and the dimension of the PRCB. The microthermal environment was mainly characterized by the local MRT and the local air temperature. The distance and the dimension would certainly affect the capability of the PRCB pair to control the microthermal environment, i.e., the ability to manipulate the local MRT and the local air temperature so as the local operative temperature to achieve individual thermal preference.

Turning to FIG. 7A, assuming the occupant was sitting in the middle of the cuboid, the local Mean Radiant Temperature (MRT) was determined by the cooling surface temperature of the PRCB pair and the temperature of other surrounding surfaces, including the walls, floor, and ceiling visible from the center of the cuboid²⁶. Mathematically, the local MRT could be estimated by:

$\begin{array}{cc}{\mathrm{MRT}}_{\mathrm{mic}}^4=\left(2{\epsilon }_c{\mathrm{ERT}}_c^4{F}_{P\to \mathrm{RCP}}+{\sum }_{j=1}^{n_{\mathrm{uc}}}{\epsilon }_j{T}_{\mathrm{uc},j}^4{F}_{P\to \mathrm{uc},j}\right)/{\epsilon }_o& \left(3\right)\end{array}$

where ERT_c was the equivalent temperature of the radiant cooling surfaces, defined as the temperature of a PRCB without the membrane and the low humidity layer that could provide the same cooling power by the membrane-integrated PRCB with the radiant cooling temperature of T_c; ε_c was the emissivity of the RCP radiant cooling surfaces; ε_o was the uniform emissivity of enclosure surface; F_P→RCP was the angle factor between the occupant and the radiant cooling surfaces; T_uc,j was the temperature of the j^th uncooled surrounding surface; and F_P→uc,j was the angle factor between the occupant and the j^th uncooled surface. Note that ERT_c was used in Equation (3) due to the coverage of the radiant cooling surface by the membrane, which was not 100% transparent for the radiative heat exchange. For the microthermal environment created by the PRCB pair, only the temperature of these two radiant cooling surfaces was under control while the others are not.

The local air temperature (T_mic) was established through convective heat exchange, as shown in FIG. 7B. The local air transferred its heat to the membrane through convection occurring on the external surface the membrane; and the membrane transferred its heat to the radiant cooling surface through convection and conduction inside the low humidity layer sealed by the membrane.

The ambient air transferred its heat to the local air through the convention occurring at the virtual surfaces. At steady state, the non-radiant heat flux between the radiant cooling surface and the membrane was equivalent to the non-radiant heat flux between the membrane and the local air, as well as to the non-radiant heat flux between the local air and the ambient air, i.e.,

$\begin{array}{cc}{Q}_c=h_{e1}{A}_{e1}\left(T_m-T_c\right)=h_{e2}{A}_{e2}\left(T_{\mathrm{mic}}-T_m\right)=h_{e3}{A}_{e3}\left(T_{\mathrm{amb}}-T_{\mathrm{mic}}\right)& \left(4\right)\end{array}$

where h_e1, h_e2, h_e3 were the equivalent heat transfer coefficients between the membrane and the radiant cooling surface, between the membrane and the microthermal environment; and between the microthermal environment and ambient environment, respectively. A_e1, A_e2, A_e3 were respectively the total area of the two radiant cooling surfaces, the two membrane surfaces, and the four virtual surfaces. A_e1 was identical to A_e2, depending on the size of the PRCB; while A_e3 was relative to the size of the PRCB as well as the distance between the two PRCBs.

Given the size of the PRCBs and the distance between the PRCB pair, a microthermal environment model was developed to predict the ERT_c, the local MRT, the local air temperature as well as the membrane temperature T_m by applying the energy balance to the membranes of the PRCBs.

$\begin{array}{cc}{q}_{\mathrm{me},\mathrm{in}}+q_{\mathrm{mi},\mathrm{in}}+h_{e2}\left(T_{\mathrm{mic}}-T_m\right)=q_{\mathrm{me},\mathrm{ot}}+q_{\mathrm{mi},\mathrm{ot}}+h_{e1}\left(T_m-T_c\right)& \left(5\right)\end{array}$

where q_me,in and q_me,ot were the heat flux into/out from the external surface of the membrane (the surface towards the occupant), respectively; q_mi,in and q_mi,ot were the heat flux into and out from the internal surface of the membrane (towards the radiant cooling surface), respectively.

With the aforementioned adjustable control strategy, the thermal comfort and energy performance of the microthermal environment created by condensation-free PRCBs can be enhanced, showcasing significant potential for promotion and application.

Example 3—Evaluation of the Prepared Microthermal Environment Model

Turning to FIG. 8, a prototype for the PRC system was constructed. Two PRCBs, each with dimensions of 1 m×0.7 m, were constructed and installed on the two sides of the thermal manikin: one on the left-hand side and the other on the right-hand side. Each was positioned 0.6 m away from the center of the manikin. A number of sensors were installed in the microthermal environment, the ambient environment, and the PRCBs to measure various thermal parameters.

For the microthermal and ambient environment, air temperature, air velocity, black globe temperature, and humidity were measured at five heights (0.1 m, 0.6 m, 0.9 m, 1.1 m, and 1.7 m). In the PRCBs, 20 calibrated T-type thermocouples were attached to the membrane and the panel surfaces, recording surface temperatures at five positions to obtain the actual temperatures at different positions. The present invention also recorded the supply and return water temperatures using four calibrated T-type thermocouples, and three flow meters were employed to test the flow rate of the supply and return water.

The ambient temperature was adjusted using electrical heaters with three power levels: fully on, half on and fully off. Table 1 summarized the main temperatures of the ambient environment, including T_amb, MRT and T_op, before and after the PRC system was switched on.

TABLE 1
Main variables of the ambient environment
Scenario	Ambient environment before PRC	Ambient environment after PRC system on
(Electrical	system on	(with Tc = 5° C.)
heater)	Tamb(° C.)	MRT (° C.)	Top (° C.)	Tamb (° C.)	MRT (° C.)	Top (° C.)
Fully on	31.3	31.3	31.3	31.0	30.9	30.9
Half on	29.2	29.5	29.4	29.2	29.3	29.3
Full off	27.7	27.7	27.7	27.4	27.4	27.4

Even when the heaters were fully off, the ambient environment was “warm” or slightly “hot” and outside of the generally thermal comfortable range (T_op=24-26° C.) defined by ASHRAE. Table 1 also showed that the PRC system had a limited capacity to affect the ambient environment. Even if the radiant cooling temperature was as low as 5° C., the ambient environment was not significantly affected. For example, there was only 0.3° C. in the air temperature difference before and after the PRC system was on.

At each scenario, the radiant cooling temperature T_c was controlled and stabilized at 5, 10, 15, and 20° C. The local MRT, local air temperature T_mic and the local operative temperature T_op at different T_c were given in FIGS. 9A-9C, respectively.

Referring to FIG. 9A, it showed that the RCP pair could effectively create a “cooling” microthermal environment in a “hot” ambient environment. For example, when the ambient temperature was 31.3° C., the RCP pair at 5° C. reduced the MRT from 31.7° C. to 27.8° C., almost 4° C. If the human body metabolic body heat was assumed to be 70 W/m², the radiative heat exchange could be enhanced by 9.7%(41.8 W/m² at MRT=31.7° C. and 46.3 W/m² at MRT=27.8° C.). Using a linear curve fitting method, the local MRT was estimated by:

$\begin{array}{cc}{\mathrm{MRT}}_{\mathrm{mic}}=0.125T_c+0.875T_{\mathrm{ew}},R^2=0.969& \left(5\right)\end{array}$

The weighting factor 0.125 for T_c showed that the regulation capability of the RCP pair on the MRT of the microthermal environment, which should be affected by the dimension of the RCPs as well the distance between the two RCPs. If the RCP was enlarged from 1 m×0.7 m to 1 m×1 m and 1 m×1.2 m, Equation (5) became MRT=0.212 T_c+0.788T_ew and MRT=0.257 T_c+0.743 T_ew, respectively. In this case, T_c=5° C. could achieve MRT=24.5° C. when the ambient temperature was 31.3° C.

The RCP pair reduced the local air temperature through the heat exchange with the membrane surface. As shown in FIG. 9B, the local air temperature was lowered from 31.3° C. to 29.2° C. by the RCP pair with 5° C., being around 2° C. This reduction was not significant, indicating that the RCP pair had a limited capacity to adjust the local air temperature of the microthermal environment. This could also be explained using the formula fitted using a least square method, shown below:

$\begin{array}{cc}{T}_{\mathrm{mic}}=0.076T_c+0.924T_{\mathrm{amb}},R_2^2=0.986& \left(6\right)\end{array}$

The weighting factor for T_c was only 0.076, much smaller than the weighting factor for T_amb(0.924), indicating that the local temperature was mainly affected by the ambient temperature.

Indeed, a large RCP pair should enhance the contribution of T_c to T_mic. For example, when the RCP was enlarged from 1 m×0.7 m to 1 m×1 m and 1 m×1.2 m, the weighting factor for T_c could be enlarged to 0.084 and 0.088 respectively. Compared to Equation (5) with (6), the RCP pair had a stronger capability to regulate the local MRT than the local air temperature.

FIG. 9C showed the local operative temperature T_mic,op of the microthermal environment when T_c was 5° C., 10° C., 15° C., and 20° C. under the ambient temperature of 31.3° C., 29.2° C. and 27.7° C. respectively. Once again, using the least square curve fitting, T_mic,op could be approximated by:

$\begin{array}{cc}{T}_{\mathrm{mic},\mathrm{op}}=0.611{\mathrm{MRT}}_{\mathrm{mic}}+0.389T_{\mathrm{mic}},R^2=0.994& \left(7\right)\end{array}$

The coefficient α=0.611, much larger than β=0.389, indicating that the contribution of the local MRT to the local operative temperature was higher than that of the local air temperature. When enlarging the dimension of the RCPs, the coefficient for MRT_mic and T_mic was not significantly changed (α=0.621, β=0.379 for the 1 m×1 m RCP pair and α=0.625, β=0.375 for the 1 m×1.2 m RCP pair).

Furthermore, the condensation risk was analyzed in FIG. 10. The dashed line represented the dew-point temperature at RH=60% for the ambient temperature of 27.7° C., 29.2° C., and 31.3° C. The temperature distribution on each RCP was non-uniform due to turbulent natural convection and buoyancy effects inside the air layer, resulting in a lower temperature at the lower part of the membrane as compared to the upper part, which would make the membrane's lower part more susceptible to condensation.

To minimize the risk of condensation, it was recommended to maintain the lower test-point membrane temperature above 20.0° C., 18.6° C., and 17.2° C. for the ambient air temperature of 27.7° C., 29.2° C., and 31.3° C., respectively. Similarly, using a linear curve fitting method, the average membrane temperature could be estimated as:

$\begin{array}{cc}{T}_m=0.382T_c+0.618T_{\mathrm{mic}},R^2=0.997& \left(8\right)\end{array}$

When the dimensions of the RCP pair were enlarged to 1 m×1 m and 1 m×1.2 m, the coefficients for T_c and T_amb remained unchanged. This was due to the fact that the coefficients were dependent on the heat transfer coefficient within the vertical air layer, which was relative to its height (H) and thickness (d). Thus, when the width of the vertical air layer was increased to enlarge the RCPs, the heat transfer coefficient within the vertical air layer remained constant.

In addition, the thermal comfort of the microthermal environment created by the RCP pair was also investigated. According to Fanger's thermal comfort theory, occupants' thermal comfort perceptions were highly relative to their metabolic rate, clothing insulation, relative humidity, air temperature, mean radiant temperature, and so on^3,7. To simply the analysis, the present invention only considered a typical scenario in offices, in which the metabolic rate was assumed to be 1.2 met (office work) and 0.5 clo for wearing (typical office wear). 24 subjects were invited to feedback their thermal sensation in the thermal environment created by the RCP pair with the radiant cooling temperature being 5° C. (cold), 10° C. (medium) and 15° C. (cool) under the ambient temperature being 28° C. (warm) and 30° C. (hot). The thermal survey was designed following the standard procedure outlined in the previous study⁷.

FIG. 11A showed an infrared camera image of a subject who was doing the thermal survey, and FIG. 11B showed the survey results. As expected, given the ambient temperature (e.g., 28° C.), the thermal sensation vote (TSV) decreased with the decrease of T_c. When T_amb=28° C., the TSV was round 0.20, −0.10 and −0.26 for T_c=15, 10 and 5° C. respectively. When T_amb=30° C., the TSV was round 1.26, 0.73 and 0.36 for T_c=15, 10 and 5° C. respectively. Even if the radiant cooling temperature was as low as 5° C., the ideal thermal situation TSV=0 was not achieved. Using the available 1880 data sets, the TSV in the microthermal environment created by the RCP pair was estimated by:

$\begin{array}{cc}\mathrm{TSV}=0.063T_c+0.414T_{\mathrm{amb}}-12.28R^2=0.986& \left(9\right)\end{array}$

If using TSV=±0.5 as the criterion for the individual thermal comfort, the radiant cooling temperature should be adjusted inside (3.0, 18.9° C.) for T_amb=28° C. and (−10.2, 5.7) for T_amb=30° C. The thermoneutral state was achieved at T_c=10.9° C. for T_amb=28° C. and at T_c=−2.2° C. for T_amb=30° C.

In the current practice of chiller plant, the chilled water supply with a temperature below 3° C. is not practical. Therefore, the RCP pair with the dimension of 1×0.7 m could not be used to achieve general thermal comfort when the ambient temperature was higher than 28° C. One simple solution to deal with potential higher ambient temperature is to use a large RCP.

FIGS. 12A-12B compared the temperature adjustment range to fulfill the TSV being inside (−0.5, 0.5) when the radiant surface dimension was 1×0.7 m, 1×1 m, 1×1.2 m, respectively. Indeed, the temperature adjustment range was increased significantly with the increase of the dimension. When T_amb=28° C., the range was changed from (3, 18.9° C.) for the RCP pair with 1×0.7 m to (14.4, 24.6° C.) the RCP pair with 1×1.2 m. Even if T_amb=30° C., the RCP pair with 1×1.2 m could achieve the thermoneutral state at a feasible chilled water supply temperature of 10° C.

When the local operative temperature was used to characterize the thermal comfort of the microthermal environment, the relationship between the TSV and the local operative temperature was illustrated in FIG. 13A. Using the experimental data, the TSV was approximated by:

$\begin{array}{cc}\mathrm{TSV}=0.508T_{\mathrm{mic},\mathrm{op}}-13.386,R^2=0.934& \left(10\right)\end{array}$

When the TSV was required to be inside (−0.5, 0.5) for typical office activities (relative humidity of 40-60%, metabolic rate of 1.2 met, and clothing insulation of 0.5 clo,), the local operative temperature should be controlled inside (25.4, 27.3° C.) This range was different when PMV was used as the thermal comfort index. Using Fangers' thermal comfort model, the local operative temperature should be controlled inside (22.6, 26.4° C.) for PMV belongs to (−0.5, +0.5), as shown in FIG. 13B. These differences indicated that the traditional Fanger's model could not suitable for the prediction of the thermal comfort of the PRC system.

Moreover, the energy-saving potential of the RCP pair was evaluated in a cooling season from April 1 to October 31 in Hong Kong. A large office with the dimension of 50 m×20 m×3.6 m was used in the analysis.

The maximum occupancy was assumed to be 100 occupants, i.e., 1 person per 10 m². Two scenarios were considered. In Scenario 1, the ambient temperature and the RH were set as 28° C. and 55.2%. The RCP pairs with 1×0.7 m were used to create individual microthermal environments. The radiant cooling temperature was set to be 10.9° C. for achieving TSV=0 at RH_mic=60%. The cooling capacity of each RCP in this scenario was 86.7 W/m², and the radiative and convective heat flux was 74.1 W/m² and 12.6 W/m² respectively.

In Scenario 2, the ambient temperature and the RH were set as 30° C. and 51.2%. The RCP pairs with 1 m×1 m were used to create individual microthermal environments, and the radiant cooling temperature was set to be 7.8° C. for achieving TSV=0 at RH_mic=60%. The cooling capacity of each RCP in this scenario was 106.8 W/m², and the radiative and convective heat flux was 89.5 W/m² and 17.3 W/m² respectively. For comparison, a conventional air-cooling system was used to condition the whole office, and the air temperature was set to 24.2° C., which could achieve PMV=0.

FIG. 14 gave the boundary conditions for the energy performance simulation, which included the heat gains from the roof, west external wall, windows, equipment, lighting, and the human body. The sensible and the latent heat gained from the equipment, such as lighting and computers, and the human bodies were dependent on a predefined work schedule. The cooling period was set to be 7 am to 11 pm from Monday to Friday and 7 am to 2 pm on Saturday, respectively³⁵.

FIGS. 15A-15B illustrated the energy-saving potential of the PRC system. In the cooling seasons, the total load of the PRC system was reduced by 16.9% and 17.3% on average in Scenario 1 and Scenario 2, respectively. It was important to note that in April, the energy-saving potential exhibited a wide range, ranging from 10% to 90%, with an average of 28.0% in Scenario 1 and 26.8% in Scenario 2. During this month, characterized by an average outdoor temperature of 21.9° C. and humidity of 82.2%, the utilization of outdoor air with lower temperatures becomes feasible in large office spaces, allowing for direct supply to meet the fresh air requirements of occupants. Consequently, the RCP pair could effectively handle the sensible heat dissipated by individuals. From May to September, the energy-saving potential was predominantly observed within a range of 10% to 25% in Scenario 1, and 10% to 35% in Scenario 2, which was comparatively lower than that observed in October (ranging from 15% to 35% in Scenario 1 and 10% to 50% in Scenario 2). The maximum energy-saving potential was achieved, with 76.7% and 84.1% for Scenario 1 and Scenario 2, respectively during periods of low occupancy (e.g., 10 persons from 7 am to 8 am and 7 pm to 11 pm). As occupancy increased (e.g., 90 persons from 9 am to 11 am and 1 pm to 4 pm), the energy-saving was reduced.

Turning to FIG. 16A, the energy-saving potential for different occupancy levels on a typical day in April was presented, which revealed a substantial average energy-saving potential of 47.3% and 41.4% for Scenario 1 and Scenario 2, respectively.

In FIG. 16B, a comparison of the energy consumption was provided for conventional air-cooling systems, PRC cooling system in Scenario 1 and PRC cooling system in Scenario 2, during a typical day in April. The dashed line represented the energy consumption of the RCP pair. Notably, when the ambient air temperature was higher (e.g., 30° C. in Scenario 2), the energy consumption of the PRC cooling system exhibited greater fluctuations in response to occupancy compared with warmer ambient air temperature (e.g., 28° C. in Scenario 1). This suggested that at a high ambient temperature, the energy was mainly consumed by the RCP pair for individual comfort requirements. Therefore, the PRC cooling system demonstrated significant energy-saving potential in office buildings with partial occupancy levels and dedicated outdoor air supply conditions.

In summary, the present invention allows individuals to regulate their microthermal environment to meet their personal thermal preferences without significantly affecting others based on the consistent radiant cooling space in a large-scale office in a hot and humid climate. It allows the use of higher ambient temperatures (e.g., >28° C.) than “one-fits-all” air-conditioning systems, which may result in significant energy savings because a 1° C. increase can achieve about 3% energy savings.

The microthermal environment created by the PRCB pair can be characterized by the operative temperature, which should be estimated by local mean radiant temperature and local air temperature. The local operative temperature T_mic,op of the microthermal environment can be calculated as T_mic,op=αMRT_mic+βT_mic. In this case, α=0.611 and β=0.389 for the RCP pair with 1×0.7 m; α=0.621 and β=0.379 for the RCP pair with 1×1 m; α=0.625 and β=0.375 for the RCP pair with 1×1.2 m. The local MRT can be predicted by MRT_mic=0.125T_c+0.875T_ew; The local air temperature can be provided by T_mic=0.076T_c+0.924 T_amb.

The thermal comfort can be estimated as TSV=0.063T_c+0.414T_amb-12.28; TSV=0.508 T_mic,op−13.386. The operative temperature comfort range is at 25.4-27.3° C. in present study (TSV=±0.5), slightly higher than that at 22.6-26.4° C. in Fanger's model (PMV=±0.5), for a relative humidity of 60%, metabolic rate of 1.2 met, and clothing insulation of 0.5 clo. The temperature adjustment range to fulfil the TSV being inside (−0.5, 0.5) can be increased by 5.7-11.4° C. and 10.5-16.3° C. at ambient temperatures of 28° C. and 30° C., respectively, when the radiant surface dimension increased from 0.7 m×1 m to 1.2 m×1 m.

The foregoing description of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations will be apparent to the practitioner skilled in the art.

The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, thereby enabling others skilled in the art to understand the invention for various embodiments and with various modifications that are suited to the particular use contemplated.

Definitions

Throughout this specification, unless the context requires otherwise, the word “comprise” or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. It is also noted that in this disclosure and particularly in the claims and/or paragraphs, terms such as “comprises”, “comprised”, “comprising” and the like can have the meaning attributed to it in U.S. Patent law; e.g., they allow for elements not explicitly recited, but exclude elements that are found in the prior art or that affect a basic or novel characteristic of the present invention.

Furthermore, throughout the specification and claims, unless the context requires otherwise, the word “include” or variations such as “includes” or “including”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

As used herein and not otherwise defined, the terms “substantially,” “substantial,” “approximately” and “about” are used to describe and account for small variations. When used in conjunction with an event or circumstance, the terms can encompass instances in which the event or circumstance occurs precisely as well as instances in which the event or circumstance occurs to a close approximation. For example, when used in conjunction with a numerical value, the terms can encompass a range of variation of less than or equal to +10% of that numerical value, such as less than or equal to +5%, less than or equal to +4%, less than or equal to +3%, less than or equal to +2%, less than or equal to +1%, less than or equal to +0.5%, less than or equal to +0.1%, or less than or equal to +0.05%.

References in the specification to “one embodiment”, “an embodiment”, “an example embodiment”, etc., indicate that the embodiment described can include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

In the methods of preparation described herein, the steps can be carried out in any order without departing from the principles of the invention, except when a temporal or operational sequence is explicitly recited. Recitation in a claim to the effect that first a step is performed, and then several other steps are subsequently performed, shall be taken to mean that the first step is performed before any of the other steps, but the other steps can be performed in any suitable sequence, unless a sequence is further recited within the other steps. For example, claim elements that recite “Step A, Step B, Step C, Step D, and Step E” shall be construed to mean step A is carried out first, step E is carried out last, and steps B, C, and D can be carried out in any sequence between steps A and E, and that the sequence still falls within the literal scope of the claimed process. A given step or sub-set of steps can also be repeated. Furthermore, specified steps can be carried out concurrently unless explicit claim language recites that they be carried out separately.

The functional units and modules of the PRCB and/or adjustable method in accordance with the embodiments disclosed herein may be implemented using computing devices, computer processors, or electronic circuitries including but not limited to application specific integrated circuits (ASIC), field programmable gate arrays (FPGA), microcontrollers, and other programmable logic devices configured or programmed according to the teachings of the present disclosure. Computer instructions or software codes running in the computing devices, computer processors, or programmable logic devices can readily be prepared by practitioners skilled in the software or electronic art based on the teachings of the present disclosure.

All or portions of the methods in accordance to the embodiments may be executed in one or more computing devices including server computers, personal computers, laptop computers, mobile computing devices such as smartphones and tablet computers.

The embodiments may include computer storage media, transient and non-transient memory devices having computer instructions or software codes stored therein, which can be used to program or configure the computing devices, computer processors, or electronic circuitries to perform any of the processes of the present invention. The storage media, transient and non-transient memory devices can include, but are not limited to, floppy disks, optical discs, Blu-ray Disc, DVD, CD-ROMs, and magneto-optical disks, ROMs, RAMs, flash memory devices, or any type of media or devices suitable for storing instructions, codes, and/or data.

Each of the functional units and modules in accordance with various embodiments also may be implemented in distributed computing environments and/or Cloud computing environments, wherein the whole or portions of machine instructions are executed in distributed fashion by one or more processing devices interconnected by a communication network, such as an intranet, Wide Area Network (WAN), Local Area Network (LAN), the Internet, and other forms of data transmission medium.

Other definitions for selected terms used herein may be found within the detailed description of the present invention and apply throughout. Unless otherwise defined, all other technical terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which the present invention belongs.

INDUSTRIAL APPLICABILITY

The present portable condensation-free PRCB has a huge market because it is of great potential in applications of office buildings with the improvement of people's living levels and personal thermal comfort requirement. Due to its flexibility in improving cooling capacity and energy efficiency, it can be used to replace conventional personalized ventilation systems and conventional personalized radiant cooling systems. It is particularly suitable for use in large-scale offices for meeting personal thermal requirements in hot and humid climates. The proposed condensation-free PRCB can also be used to retrofit existing PRCS for enhancing cooling capacity.

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Claims

1. A portable condensation-free temperature-adjustable radiant cooling board system comprising

a supporting panel, the supporting panel having a multi-layer structure comprising: at least one water pipe layer covered with at least one thermally-conductive conforming layer; at least one insulation layer on one side of the at least one water pipe layer; at least one high emissivity radiative layer on the other side of the at least one water pipe layer, the high-emissivity radiative layer creating a radiant cooling surface with an adjustable temperature range between 5° C. and 20° C.; at least one low humidity layer in front of the at least one high emissivity radiative layer, sealed by an infrared-transparent membrane over a radiant cooling surface in conjunction with at least one side frame, with desiccant materials positioned on the at least one side frame to maintain dryness within the air-layer, the low humidity layer having a humidity of less than 35% such that the radiant cooling board system does not generate condensation;

a movable stand holding the supporting panel; and

an angle-adjuster for user-selected change of a facing angle (θ) of the supporting panel towards the user.

2. The condensation-free temperature-adjustable radiant cooling board system of claim 1, wherein the at least one water pipe layer comprises supply fluid capillaries and return fluid capillaries.

3. The condensation-free temperature-adjustable radiant cooling board system of claim 1, wherein the at least one high emissivity radiative layer is a thin metal layer coated with a high emissivity radiative paint.

4. The condensation-free temperature-adjustable radiant cooling board system of claim 3, wherein the thin metal layer has a thickness in a range of 0.08-0.10 mm.

5. The condensation-free temperature-adjustable radiant cooling board system of claim 3, wherein the at least one high emissivity radiative layer comprises a graphene carbon nanotube coating with an emissivity of 0.95-0.98.

6. The condensation-free temperature-adjustable radiant cooling board system of claim 1, wherein the infrared transparent membrane has a thickness of 0.015-0.02 mm.

7. The condensation-free temperature-adjustable radiant cooling board system of claim 1, wherein the infrared transparent membrane is made from pure low-density polyethylene (LDPE).

8. The condensation-free temperature-adjustable radiant cooling board system of claim 1, wherein the infrared transparent membrane has a transmittance rate of at least 80% for infrared waves within the wavelength range of 2.5-22 μm.

9. The condensation-free temperature-adjustable radiant cooling board system of claim 1, wherein the low humidity layer has a thickness ranging from 5-10 cm.

10. The condensation-free temperature-adjustable radiant cooling board system of claim 1, wherein the facing angle (θ) is in a range of 60-90 degrees.

11. The condensation-free temperature-adjustable radiant cooling board system of claim 1, wherein the portable condensation-free temperature-adjustable radiant cooling board system has an inlet for receiving chilled water and an outlet for returning the water to a chiller.

12. A method for accommodating diverse individual thermal comfort preferences in hot and humid climates, comprising installing at least one condensation-free temperature-adjustable radiant cooling board system of claim 1 on each side of a user to create a microthermal environment, wherein a distance between the condensation-free temperature-adjustable radiant cooling board system and the user is defined as “D”, and the D is in a range of 60-90 cm, and wherein the supporting panel is mounted on a movable stand, and an angle-adjuster is used for user-selected change of a facing angle (θ) of the supporting panel towards the user.

13. The method of claim 12, wherein the facing angle (θ) is in a range of 60-90 degrees.

14. The method of claim 12, wherein a radiant cooling surface on the condensation-free temperature-adjustable radiant cooling board has a temperature ranging between 5° C. and 20° C. when utilizing the supporting panel.

15. The method of claim 12, further comprising introducing supply water and return water into the at least one condensation-free temperature-adjustable radiant cooling board system.