High-low speed control algorithm for direct expansion air-conditioning systems for improved indoor humidity control and energy efficiency

Abstract

The present invention relates a method of dehumidifying an enclosed environment with a direct expansion air conditioning system, such direct expansion air conditioning system containing a two speed compressor and a two speed supply fan that allows the compressor and supply fan to run at high speeds in a steady-state or low speeds in a steady-state for better humidity control. Such a system allows for a more efficient, less costly system in comparison to single speed direct expansion air conditioner or direct expansion air conditioners with variable speed compressors and supply fans.

Description

BACKGROUND

The use of direct expansion air conditioning systems has many advantages, including being simple to configure, more energy efficient, and is generally less costly to maintain than other types of air conditioning systems. However, most direct expansion air conditioning systems are equipped with single-speed compressors and supply fans, relying on On-Off cycling as a low-cost approach to maintain indoor dry-bulb temperature but not addressing indoor air-humidity. As such, in an On-Off system, when the cooling effect of the air conditioner is stopped, any dehumidification effect is also stopped. In humid environments, the requirement for continuing dehumidification is often more important than cooling.

The introduction of variable frequency inverters has made the speed control of electric motors more practical. The use of variable speed supply fans and compressors in air conditioners for controlling temperature and humidity has been investigated. Experimental results suggest that varying speeds of both compressor and supply in a direct expansion air conditioner system can help control humidity, however the incorporation of variable speed compressors and supply fans has proven to be complicated and costly, raising the price of direct expansion air conditioners with variable speed compressors and supply fans to many times that of direct expansion air conditioners with single speed compressors and supply fans.

The art has failed to develop direct expansion air conditioners with multiple speed compressors and supply fans to address temperature and humidity while still maintaining the cost effectiveness of the system.

It is an object of the present system to overcome these and other disadvantages in the prior art.

The present system proposes a direct expansion air conditioner possessing a multiple speed compressor and supply fan that is suitable for addressing cooling and dehumidification while maintaining the cost effectiveness of the system.

The present system also teaches a control method for using a direct expansion air conditioner possessing a multiple speed compressor and supply fan.

DETAILED DESCRIPTION

These and other features, aspects, and advantages of the apparatus and methods of the present invention will become better understood from the following description, appended claims, and accompanying drawings where:

FIG. 1 shows an apparatus used in conjunction with the present method.

FIG. 2 shows an embodiment of the present method.

FIG. 3 is a schematic of an air-conditioner system useful for the present method.

FIG. 4 sets forth the algorithms for the present method (Test A1) and current algorithms used in the art (Test A2-A5).

FIG. 5 shows the results of the indoor air dry-bulb temperature for A1 and A2-A5.

FIG. 6 shows results of the indoor air relative humidity for A1 and A2-A5.

FIG. 7 shows the performance data for A1 and A2-A5.

The following description of certain exemplary embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. Throughout this description, the term “air conditioner” refers to a device for the cooling and often dehumidification of air in an enclosed environment.

The term “steady-state” refers to a state at which an observed behaviour of the system will continue into the future. In general, a steady state is not achieved until some time has elapsed after the system is started or initiated.

The term “RPM” refers to revolutions per minute and relates to a measurement of rotational speed.

The term “high-low speed control” refers to in direct expansion (DX) air conditioner, the refrigerant flow rate and supply air flow rates are principally determined by the rotational speeds of the compressor and the supply fan.

FIG. 1-7 show embodiments of the present method.

FIG. 1 is an example of an apparatus 100 suitable for use in the present method containing a refrigeration plant possessing a compressor 101, a direct expansion evaporator 103, an expansion valve 107, a condenser 105, controllers 106, and an air-distribution sub-system made of ductwork 111, a supply fan 113, an air filter 117, said method to be used for an enclosed environment 120.

The apparatus 100 as used in the present method is an air conditioner, such as a window unit, through the wall unit, portable air conditioner, central air conditioner, or mini-split air conditioner. The apparatus 100 can be designed based upon the requirements of the enclosed environment 120, such as adjustments for size, power input, power output as measured in BTU's, length of ductwork, size of ductwork, and positioning of apparatus 100 within the environment 120.

The compressor 101 used in the present method is a two speeds vapor refrigerant compressor capable of operating at a high speed and a low speed. High speed of the compressor 101 can be the compressor's continuous top speed in terms of revolutions per minute, continuous referring to the compressor's ability to maintain the speed in a steady-state condition. In one embodiment, the high speed is the full speed of the compressor 101. Low speed of the compressor 101 is when the compressor is operating at a percentage less than the high speed, for example the low speed may be a speed that is 40% of the high speed. In other embodiments, the low speed is a speed that is 50% of the high speed. In still other embodiments, the low speed is a speed that is 60% of the high speed. Suitable compressors may operate in a supply frequency of from 30 Hz to 90 Hz, and operate at a speed of between 1800 to 6500 revolutions per minute (RPM). When the compressor 101 is two speed, the high speed and the low speed are set, i.e., in normal operation the speeds do not vary. For example, the high speed may be set at 6000 RPM and the low speed is set at being 60% of the high speed (3600 RPM). The compressor can be a rotor compressor, such as a vane-type, lobe-type, liquid seal ring type, a reciprocating compressor, such as a hermetic-type, semi-hermetic type, or open-type, a wobble plate compressor, such as an electronically controlled variable displacement, or a scroll compressor. Example of a commercially available suitable compressors include Bristol® H2NG series two speed compressors.

The direct expansion evaporator 103 can contain direct expansion evaporating coils (not shown). Suitable evaporator coils may be made of stainless steel, galvanized steel, aluminum, copper, contain connections, distributors, thredded connections; fins for attachment to such coils may be aluminum or copper, and be spaced from 10 to 22 fins per inch, from 10 to 16 fins per inch, from 4 to 16 fins per inch, and include circuitry. In one embodiment, the fins are stacked and spaced apart, whereas the coils are equidistant from each other. In a further embodiment, the fins and coils possess an anti-corrosive coating. The coils as taught in U.S. Pat. No. 4,089,368, incorporated herein by reference, are suitable for use in the present method.

The refrigerant (not shown) to be cycled throughout the apparatus 100 can be selected from the group consisting of HCFC, such as chlorodifluoromethane (R-22); Azetropic mixtures such as R-410A; R-134c; R-409C; and liquid propane gas (R-290). Other suitable refrigerants can be selected from R-10, R-11, R-12, R-12B1, R-12B2, R-13, R-13B1, R-14, R-20, R-21, R-22B1, R-23, R-30, R-31, R-3, 2R-40, R-41, R-50, R-110, R-111, R-112, R-112a, R-113, R-113a, R-114, R-114a, R-114B2, R-115, R-116, R-120, R-121, R-122, R-123, R-124, R-124a, R-125, R-E125, R-130, R-131, R-132B, R-132bB2, R-133a, R-134, R-E134, R-140a, R-141B2, R-141b, R-142b, R-143a, R-152a, R-160, R-170, R-211, R-212, R-213, R-214, R-215, R-216, R-217, R-217ba, R-218, R-221, R-222, R-223, R-224, R-225CA, R-225CB, R-226, R-227ca, R-227ea, R-231, R-232, R-233, R-234, R-235, R-236cb, R-236ea, R-236fa, R-FE-36, R-241, R-242, R-243, R-244, R-245ca, R-245cb, R-245ea, R-245eb, R-245fa, R-251, R-252, R-253, R-254cb, R-261, R-262, R-271, R-C316, R-C317, R-C318, R-329 ccb, R-338eea, R-347 ccd, R-356mcf, R-356mffm, R-400, R-401A, R-401B, R-401C, R-402A, R-402B, R-403A, R-403B, R-404A, R-405A, R-406A, R-407A, R-407B, R-407C, R-408A, R-409A, R-410B, R-411A, R-411B, R-412A, R-414A, R-414B, R-417A, R-422A, R-422B, R-500, R-501, R-502, R-503, R-504, R-505, R-506, R-507, R-508, R-509, R-600, R-600a, R-610, R-611, R-630, R-631, R-702, R-704, R-717, R-718, R-720, R-728, R-732, R-740, R-744, R-744A, R-764, R-1112a, R-1113, R-1114, R-1120, R-1130, R-1132, R-1140, R-1141, R-1211, R-1216, R-1270, R-1301, and R-2402.

The expansion valve 107 for use in the present method is used to keep the pressure difference between the high and low pressure sides of the apparatus 100, and to maintain current flow of the refrigerant. Suitable expansion valves are well-known in the art, and can include thermostatic expansion valve, injection valve, or electronic expansion valve. In one embodiment, the expansion valve is an electronic expansion valve.

The condenser 105 for use in the present method operates by being subjected to a flow of air to absorb discharged heat. Suitable condensers include evaporating condenser, remote air-cooled condensers, and air-cooled condensers.

Alternatively, in the refrigeration plant, the compressor 101 and the condenser fan 105 may be controlled by a variable frequency drive (VFD) (106). The VFD 106 can contain a controller, driver, and operator interface. As used in the apparatus 100, the VFD assists in controlling the operation of the compressor 101 and condenser 105.

The ductwork 111 as used herein is properly sized according the desired properties of the enclosed environment. As will be well-known to one with skill in the art, the ductwork may be designed according to the Velocity Method (i.e., A=q/v, where A=duct cross sectional area (rn²), q=air flow rate (m³/s), and v=air velocity (m/s)), Constant Pressure Loss Method (or Equal Friction Method)(i.e., proper velocity is selected in the main duct close to the fan; pressure loss in the main duct are then used as a template for the rest of the system; the pressure (or friction) loss is kept at a constant level throughout the system), or Static Pressure Recovery Method (i.e., secondary and branch ducts are selected to achieve more or less the same static pressure in front of all outlets or inlets). The ductwork 111 may be made of aluminium.

The supply fan 113 as used herein is used for moving air around the apparatus 100 and the enclosed environment. Suitable fans include centrifugal propeller axial, tube axial, tubular centrifugal, or vane axial. The supply fan 113 can be variable speed, or two speed. In one embodiment, the supply fan 113 is a two speed centrifugal fan. The supply fan 113 can operate at a frequency of 50 Hz or 60 Hz, and can operate at a speed of between 1000 RPM and 5000 RPM. In the case where the supply fan 113 is two speed, the supply fan 113 is capable of a high speed and a low speed. The high speed of the supply fan 113 refers to the top speed the supply fan 113 is capable of operating at in a steady-state. In one embodiment, the high speed is the full speed of the fan. The low speed of the supply fan 113 is when the supply fan 113 is operating at a percentage speed of the high speed. For example, the low speed can be when the supply fan 113 is operating at 40% of the high speed. In other embodiments, the low speed is when the supply fan 113 is operating at 50% of the high speed. In still other embodiments, the low speed is when the supply fan is operating at 60% of the high speed. When the supply fan 113 is two speed, the high speed and the low speed are set, i.e., in normal operation the speeds do not vary. For example, the high speed may be set at 4000 RPM and the low speed is set at being 40% of the high speed (1600 RPM).

In the present apparatus 100 and method, the low speed does not include the apparatus 100 turning off, but rather the compressor and/or the supply fan operate at lower speed as indicated above.

The air filter 117 as used in the present apparatus 100 is used for removing synthetic dust from the air, and removing particulate and gaseous material from the air stream. The filter 117 can be reusable or replaceable. The filter 117 can be made of paper, polyester including fiberglass, foam, cotton, or oil bath.

The damper 115 as used in the apparatus 100 can be a plate or membrane damper and be rated as class 1, class 2, or class 3.

The apparatus 100 can be operationally connected to a measuring device, such as an air dry-bulb temperature sensor, air wet-bulb temperature sensor, or hygrometer. One or more measuring devices may be used in conjunction. The air dry-bulb temperature sensor is a device for measuring the air temperature apart from measuring the moisture in the air. The air dry-bulb temperature sensor may be a thermometer exposed to the air but shielded from radiation. The air wet-bulb temperature sensor is a device for measuring the temperature of adiabatic saturation in the environment. Hygrometers, such as psychrometers, sling psychrometers, or dew point hygrometers, are suitable for determining the humidity of the environment. Information from the measuring can be communicated via wired or wireless means such as infrared, or radio frequency. In one embodiment, information from the measuring device is passed to a control mechanism (not shown).

Alternatively, in the air-distribution system, the supply fan 113 may be controlled by a variable frequency drive (VFD) (106). The VFD 106 can contain a controller, driver, and operator interface. As used in the apparatus 100, the VFD 106 assists in controlling the operation of the supply fan 113.

A control mechanism (not shown) may be connected to the apparatus 100 via communication means such as wired or wireless means including radio frequency or infrared. The control mechanism may also be connected to the measuring device via wired or wireless means. In one embodiment, the control mechanism acts as a connection medium between the measuring device and the apparatus 100 whereby information is sent from the measuring device through the control mechanism to the apparatus 100. The control mechanism can contain a microprocessor, storage medium, such as memory, and user interfaces such as a keyboard, buttons, knobs, a display, and a power supply. The control mechanism is suitable for operating the parameters of the apparatus 100, including changing the speed of the compressor and the supply fan from high speed to low speed, and vice versa. The compressor and the supply fan may be controlled sequentially. The control mechanism is also suitable for communicating with the measuring devices, including establishing set points and reading the measurements. The control mechanism may have stored on its memory algorithms including databases, comparison algorithms, and speed adjustment algorithms. The control mechanism can be, for example, a laptop computer, handheld PDA, desktop computer, or control panel. The control mechanism may be wall-mounted or portable. The control mechanism can also include multiple remote units allowing control of the apparatus 100 and/or measuring devices from various locations.

The enclosed environment 120 wherein the apparatus 100 will be used can be a single unit structure, such as a bedroom, a multiple unit structure, such as a multiple room apartment containing various rooms, or a larger standing structure such as a five-story building. In the case where the enclosed environment 120 is a large standing structure, the apparatus 100 may be positioned on the roof or top of the structure. In the case where the environment 120 is a single unit, the apparatus 100 may be positioned within the environment in which it will operate. The positioning of the apparatus 100 can be based on the requirements of the environment 120 and such positioning is well known in the art.

FIG. 2 is an embodiment of the present method, wherein a set point is established for the enclosed environment 201, a measurement for the enclosed environment is taken 203, a comparison is made between the measurement for the enclosed environment and the set point 205, and a determination is made whether both the compressor and supply fan will operate at their high speed 209 or at their low speed 207.

The set point may be established for the enclosed environment 201 manually or automatically. The set point refers to the point at which a critical change within the environment has been reached. Going above the set point will initiate a series of events to return the environment's conditions below the set point. The set point can be a specific temperature, a specific relative humidity, a specific energy level, a temperature range, a humidity range, or an energy level range. One or more set points can be set, likely through the use of one or more measuring devices placed in the environment. For example, if a specific relative humidity is established as the set point, when the actual relative humidity in the environment is above the set point relative humidity, a series of events will be activated to return the actual relative humidity below the set point relative humidity. In manually establishing the set point, a user may interact with a measurement device located within the environment. For example, a user may set a temperature on the measurement device at 24° C., which will be the set point. Alternatively, the user may establish the set point on the measuring device using the control mechanism, such as a PDA. The control mechanism, in communicating with the measuring device, will then establish the set point on the measuring device. In automatically establishing the set point, the control mechanism may establish a set point based upon a number of factors, such as time of the day, time of the year, or a particular season. Upon reaching a certain factor, the control mechanism would then automatically communicate with the measuring device to establish the set point. The control mechanism may be programmed by a user to accomplish this automatic operation.

In one embodiment, the set point is based on air dry-bulb temperature. In another embodiment, the set point is based on air wet-bulb temperature and air dry-bulb temperature.

Upon establishing the set point, the set point is then stored onto the memory of the control mechanism for inclusion in to later algorithms.

Taking the measurement for the enclosed environment 203 can involve taking the temperature, humidity, energy level, or temperature range, humidity range, or energy level range. One or more measurements may be taken at one time. The measurement shall reflect the measuring device, for example if the measuring device is a thermometer, the measurement will be in ° C. or ° F. The measurement is taken by the measuring device which is located somewhere within the environment. In one embodiment, various measurements are taken from various measuring devices dispersed throughout the environment.

Following the taking of the measurement 203, the measurement is passed to the control mechanism. Passing of the measurement can occur by wired or wireless means. Upon passage of the measurement to the control mechanism, the measurement is stored on the memory of the control mechanism for inclusion in to later algorithms.

The control mechanism will then determine whether the measurement is above the set point 205. This is done by inserting into a comparison algorithm stored on the memory of the control mechanism both the set point and the actual or taken measurement. The comparison algorithm can be based on an “IF” “THEN” standard, for example

IF actual measurement is above set
point
THEN run compressor and supply fan at
high speed,
or;
IF actual measurement is below set
point
THEN run compressor and supply fan at
low speed.

The comparison algorithm may include a deviation such that if the actual measurement is within a range of the set point plus or minus several points, the critical condition for the set point will be determine to not have been met. For example, the deviation may be plus or minus 1. In one embodiment, the deviation may be plus or minus 0.1 to 0.5. Depending on the result of the comparison algorithm, the control mechanism will then initiate start of the compressor and supply fan, and the compressor and supply fan will run until the steady-state of the compressor and supply fan are reached, such steady-state speed to be either high (209) or low (207), as previously defined. The steady-state speed of the compressor and supply fan can be based upon the outcome of the comparison algorithm. The steady-state speed of the compressor will be either high speed or low speed, as defined previously.

The running of both the compressor and supply fan speeds at a high value and a low value, respectively, aims to achieve improved control over both indoor air temperature and relative humidity, at a higher overall energy efficiency. When the compressor is operated at a high speed, the supply fan is also operated at a high speed. When however the compressor is operated at a low speed, so is the supply fan speed. Therefore the method of control as used herein has been termed as high-low speed control.

Running both the compressor and supply fan at a high speed implies a high output cooling capacity and a high supply air flow rate; and running both the compressor and supply fan at a low speed implies a low output cooling capacity and a low supply air flow rate. The improved control over both indoor air temperature and relative humidity via high-low speed control is realized through the switch of high-low output cooling capacity-supply air flow rate. Hence the proposed method of control would cover all means which ultimately result in high-low output cooling capacity-supply air flow rate, such as high-low speed or high-low capacity adjustment through parallel-serial connection of cylinder in a reciprocating compressor.

Throughout the operation of the apparatus, the measuring device will continue to measure and pass the measurements to the control mechanism for insertion into and determination by the comparison algorithm. In the event that the measurement falls below that of the set point, the control mechanism will activate the compressor and supply fan such that they decrease their speed to the low speed steady-state. For example, the control mechanism will activate the compressor and supply fan to operate at a steady-state of 50% and 30% of the full speed, respectively.

As before, the measuring devices will continue to measure the environment. If the measurement goes above the set point, the control mechanism will activate the compressor and supply fan appropriately. If the measurement goes below the set point, the control mechanism will activate the compressor and supply fan appropriately.

FIG. 3 is a schematic of an apparatus suitable for use in the present method, comprising a direct expansion cooling coil 301, a condensing unit 303, a supply fan 307 with a variable frequency drive 309, an enclosed environment 311, data acquisition and control units 313, dampers 315, an air filter 317, a load generating unit 319, ductwork 321, measuring devices 323 including air wet-bulb temperature sensors, air dry-bulb temperature sensors, air humidity meter and air static pressure sensor.

EXAMPLE

An air conditioning system was setup, including a direct expansion apparatus containing a two speeds rotor compressor, an electronic expansion valve, an air-cooled tube plate finned condenser, a direct expansion evaporator, and an air distribution system including ductwork, return air dampers, two speeds centrifugal supply air fan, and an enclosed environment. Measuring devices were inserted into the enclosed environment, including an air wet-bulb thermometers and an air dry-bulb thermometers, and a hygrometers. A control mechanism was included. The control mechanism provided 48 channels for monitoring various types of operating parameters. The direct current signal obtained from various measuring devices and sensors could be scaled into their real and physical values of the measured parameters using logging and control supervisory algorithms. The control mechanism also included comparison algorithms.

FIG. 4 shows the parameters set for the experiment. With the high-low (H-L) system of the present method (A1) including setting the high speed of the compressor to operate at 4488 RPM, the high speed of the supply fan to operate at 3312 RPM, the low speed of the compressor to operate at 64.7% of the high speed (2904 RPM), and the low speed of the supply fan to operate at 37.9% of the high speed (1256 RPM). Alternate systems (On-Off systems) were set-up for comparison to the H-L system, the systems being based upon on-off compressors and on-off fans (A2, A3, A4, and A5). The power inputs to the various systems were as follows: sensible load 3.06 kW, and latent load 0.26 kW. The set point in the enclosed environment was established at 26° C. The comparison algorithm included a percentage deviation from the set point, such that if the measurement fell between 25.65° C. and 26.35° C., the control mechanism would not adjust the compressor speed or fan speed to a high or low speed.

The performance comparison for the direct expansion system between under On-Off control and H-L control was based on indoor air parameters such as temperature or relative humidity and the time averaged energy efficiency of the experimental direct expansion system in its last operation cycle during all tests. An operation cycle for the direct expansion system is defined as, when under H-L control, the time period required for a complete High and Low compressor speed operation cycle, and when under On-Off control, the time period required for a complete compressor on and off cycle. The last operation cycle in each test was used as the basis for evaluating energy efficiency, when the direct expansion system was considered to operate at a steady-state condition at its last operation cycle. In all tests, indoor relative humidity was not controlled, but allowed to fluctuate, depending on actual latent output cooling capacity from the direct expansion system.

FIG. 5 shows the experimental results of the dry bulb temperature. It can be seen that the range of temperature fluctuation in A1 was the smallest, but with the largest number of operation cycle. In A2, the upper limit of temperature fluctuation was 0.5° C. higher than that in A1. However, when the supply fan operated at low speed when the compressor was stopped, the fluctuation range reduced in A3. The temperature fluctuation ranges in A4 and A5 were similar to those in A2 and A3, respectively. However, the On periods in A4 and A5 were much longer than those in A2 and A3, suggesting more energy use in A4 and A5.

FIG. 6 shows the experimental results of the indoor air relative humidity (RH). It can be seen that the RH fluctuation range in A1 was around 5%, which was small when compared to those in A2 and A3, at around 20% and 10%, respectively. In addition, the indoor RH level was reduced during the low speed period, suggesting that the dehumidifying ability of the direct expansion system during the low speed period was even better than that during the high speed period. This resulted in RH in A2 being below 50%. The experimental results thus proved that the use of high speed and low speed control would lead to a better dehumidifying ability of the direct expansion system than previously expected, so that an appropriate indoor humidity level may be maintained.

FIG. 7 is a chart showing the energy performance of the last operation cycle in each test. Every test lasted for more than four hours and consisted of between 3 and 15 operation cycles. The last operation cycle in each test was used as the basis to calculate the energy performance. The means power input to the direct expansion system was calculated by time averaging power input in both the high speed and low speed periods for H-L control; and in both the On- and Off-periods for On-Off control in the last operation cycle. For example, in the last operation cycle in A1, the high speed period lasted for 375 s, during which the power input to the compressor was 2614W; and the low speed period 381 s and the power input to the compressor was 1615W, respectively. The mean c-p in A1 was then calculated as:

Mean c-p=2614*375/(375+381)+1615*381/(375+381)=2111W

The mean c-p under H-L control was the lowest, notwithstanding the fact that the c-p in an Off-period under On-Off control was zero.

If the power input to the supply fan was also accounted for in comparing the energy performance, the advantage of using the H-L control becomes more obvious due to the shorter duration of an H-period. The mean total power inputs to the direct expansion system under H-L control in A1 is 18%, lower than those under On-Off control in A3, where the power inputs to the direct expansion system under On-Off control were the lowest.

Having described embodiments of the present system with reference to the accompanying drawings, it is to be understood that the present system is not limited to the precise embodiments, and that various changes and modifications may be effected therein by one having ordinary skill in the art without departing from the scope or spirit as defined in the appended claims.

In interpreting the appended claims, it should be understood that:

a) the word “comprising” does not exclude the presence of other elements or acts than those listed in the given claim;

b) the word “a” or “an” preceding an element does not exclude the presence of a plurality of such elements;

c) any reference signs in the claims do not limit their scope;

d) several “means” may be represented by the same item or hardware or software implemented structure or function;

e) any of the disclosed elements may be compromised of hardware portions (e.g., including discrete and integrated electronic circuitry), software portions (e.g., computer programming), and any combination thereof;

f) hardware portions may be comprised of one or both of analog an digital portions;

g) any of the disclosed devices or portions thereof may be combined together or separated into further portions unless specifically stated otherwise; and

h) no specific sequence of acts or steps is intended to be required unless specifically indicated.

Claims

1. A direct expansion air conditioner for controlling indoor air humidity in an environment, comprising

a two speed compressor;

an expansion valve;

a condenser;

a two speed supply fan; and

a direct expansion evaporator containing direct expansion coils.

2. The direct expansion air conditioner in claim 1, further comprising one or more variable frequency drivers.

3. An air conditioning system for controlling the indoor humidity of an environment, comprising

a refrigeration plant containing a two speed compressor, a direct expansion evaporator containing direct expansion coils, an expansion valve, a condenser, and a refrigerant;

an air distribution network containing ductwork, a two speed supply fan, an air filter, and a damper;

a control mechanism containing a microprocessor, user interface, power supply, communication means, memory, and algorithms;

one or more measuring devices;

and an enclosed environment.

4. The air conditioning system in claim 3, wherein said two speed compressor is a rotor compressor.

5. The air conditioning system in claim 3, wherein said algorithm on said control mechanism includes a comparison algorithm.

6. The air conditioning system in claim 3, wherein said measuring devices includes an air dry-bulb, a wet dry-bulb, and a hygrometer.

7. The air conditioning system in claim 3, wherein said enclosed environment is an apartment.

8. A method of dehumidifying an enclosed environment with a direct expansion air conditioner, comprising,

establishing one or more set points in said enclosed environment;

taking measurements from one or more measuring devices located within said enclosed environment;

storing said set points and said measurement on a memory of a control mechanism;

determining whether said measurement is above said set point in accordance with the following manner IF measurement is above said set point THEN run a two speed compressor at high speed; and

maintaining said high speed of said two speed compressor in a steady-state.

9. The method of claim 8, further comprising the step of determining whether said measurement is below said set point in accordance with the manner

IF measurement is below said set point

THEN run a two speed compressor at low speed; and

maintaining said low speed of said two speed compressor in a steady-state.

10. The method of claim 9, further comprising the step of determining whether said measurement is above said set point in accordance with the following manner and

IF measurement is above said set point, THEN run

a two speed supply fan at high speed;

maintaining said high speed of said two speed supply fan in a steady-state.

11. The method of claim 10, further comprising the step of determining whether said measurement is below said set point in accordance with the following manner and

IF measurement is below said set point, THEN run

a two speed supply fan at low speed;

maintaining said low speed of said two speed supply fan in a steady-state.

12. The method of claim 9, further comprising continuing collecting measurements from said measuring devices and

adjusting said compressor based on previous determining manner.

13. The method of claim 12, further comprising the steps of continuing collecting measurements from said measuring devices, and

adjusting said supply fan based on previous determining manner.

14. The method of claim 8, wherein establishing said set points includes establishing a desired humidity on a measuring device located within said environment.

15. The method of claim 8, wherein establishing said set point includes establishing an air-dry temperature and an air-wet temperature on one or more measuring devices located within said environment.

16. The method of dehumidifying in claim 8, wherein storing said set points and measurements occurs through communication means.

17. The method of dehumidifying in claim 8, wherein determining whether said measurement is above said set point occurs via a comparison algorithm stored on a control mechanism.

18. The method of dehumidifying in claim 17, wherein determining whether said measurement is above said set point occurs via said comparison algorithm allows for a deviation between said measurement and said set point from 0.1 to 0.5 points.

19. The method of dehumidifying in claim 8, wherein maintaining said low speed of said two speed compressor means maintaining said speed at 50% of said high speed.

20. The method of dehumidifying in claim 10, wherein maintaining said low speed of said two speed supply fan means maintaining said speed at 50% of said high speed.