Abstract: A thermal management system that includes an open-circuit refrigeration system having an open-circuit refrigerant fluid flow path is described. The open-circuit refrigeration system includes a receiver configured to store a refrigerant fluid, an evaporator configured to receive the refrigerant fluid at a evaporator inlet and to extract heat from a heat load that contacts the evaporator, and provide refrigerant vapor at a evaporator outlet. The open-circuit refrigeration system also includes a vapor pump device having a vapor pump inlet that receives the refrigerant vapor and having a vapor pump outlet that outputs compressed refrigerant vapor to an exhaust line coupled to the vapor pump outlet, with the receiver, the evaporator, the vapor pump device, and the exhaust line connected in the open-circuit refrigerant fluid flow path.

Abstract: A heat exchanger includes a liquid reservoir configured to separate a gas-liquid two-phase refrigerant flowing out of an upstream heat exchanging portion into a gas-phase refrigerant and a liquid-phase refrigerant, and a refrigerant adjustment portion configured to adjust an outflow state and an outflow destination of the refrigerant flowing out of a downstream heat exchanging portion or the liquid reservoir. The liquid reservoir includes a liquid reserving portion configured to store the liquid-phase refrigerant and a gas reserving portion configured to store the gas-phase refrigerant. The refrigerant adjustment portion faces the liquid reserving portion across the gas reserving portion.

Abstract: A thermoelectric generating system for a vehicle, the thermoelectric generating system includes an engine for producing power, a thermoelectric module for producing electric energy from thermal energy of an exhaust gas generated by the engine, a purifying device for purifying the exhaust gas generated by the engine, and a controller for driving the thermoelectric module when a temperature of the purifying device arrives at a predetermined operational temperature.

Abstract: A system and method for controlling passive soot oxidation in a diesel particulate filter that includes sensing the temperature of exhaust gases upstream and downstream of the diesel particulate filter. The sensed temperatures are used by a control unit to predict whether the temperature of the exhaust gas within the diesel particulate is within a predetermined temperature range for passive oxidation of soot in the diesel particulate filter. If the temperatures are below passive oxidation temperatures, an auxiliary component is activated that increases the temperature of exhaust gas delivered to the diesel particulate filter. When the exhaust gas temperature within the DPF is predicted to be within passive oxidation levels but below active regeneration temperatures, the auxiliary component is deactivated.

Abstract: Power plant systems and methods are presented. The power plant includes a steam turbine configured to release exhaust steam. The power plant further includes an electro-hydrodynamic system operatively coupled to the steam turbine. The electro-hydrodynamic system is configured to receive the exhaust steam from the steam turbine and generate auxiliary electric power using the exhaust steam.

Abstract: Systems for regenerating an absorbent solution include steam produced by a boiler; a set of pressure turbines fluidly coupled to the boiler for receiving the steam, wherein the set of pressure turbines comprises a high pressure turbine, a medium pressure turbine and a low pressure turbine; and a regenerating system comprising a regenerator for regenerating a rich and/or semi-rich absorbent solution to form a lean absorbent solution in fluid communication with a reboiler, the regenerating system fluidly coupled to the set of pressure turbines, wherein steam from the low pressure turbine provides a heat source for preheating the rich or the semi-rich absorbent solution fed to the regenerator. Also disclosed are processes of use.

Abstract: A Rankine cycle waste heat recovery system uses a receiver with a maximum liquid working fluid level lower than the minimum liquid working fluid level of a sub-cooler of the waste heat recovery system. The receiver may have a position that is physically lower than the sub-cooler's position. A valve controls transfer of fluid between several of the components in the waste heat recovery system, especially from the receiver to the sub-cooler. The system may also have an associated control module.

Abstract: An exhaust gas collection system for capturing the exhaust gas emitted by auxiliary engines, auxiliary boilers and other sources on an Ocean Going Vessel (OGV) while at berth or at anchor, so that these gases may be carried to an emissions treatment system for removal of air pollutants and greenhouse gases. The exhaust gas collection system includes a diverter to redirect the exhaust gas normally carried by exhaust pipes to the OGV's stack for release to the atmosphere, to an exhaust gas treatment system. The emissions treatment system may be land-based, water-based, or on the OGV. When the emissions treatment system is land-based, water-based, the exhaust gas is carried to a connection location that accessible by a ducting system to carry the exhaust gas to the emissions treatment system. The exhaust gas collection system preferably includes parallel-flow ducts and a manifold to combine the parallel-flows into a single duct for more convenient routing through the vessel.

Abstract: An exhaust system is provided for mitigating condensate formation in a common exhaust stack and for effecting improved heat transfer. Reduced condensate formation and improved heat transfer is achieved by inducing non-laminar flow through the common exhaust stack and a heat exchanger operatively coupled to the common exhaust stack. Heat transfer is further improved by dew point control. Non-laminar flow is induced by connecting more than one gas turbine to the common exhaust stack through non-laminar flow inducing arrangements. The various coupling arrangements also add structural rigidity to the common exhaust stack for increased stack height and improved plume dispersion.

Abstract: An engine and one or more aftertreatment subsystems integrated into one system for optimization and control. At least one controller may be connected to the engine and the one or more aftertreatment subsystems. The controller may contain and execute a program for the optimization and control of the one system. Controller may receive information pertinent to the engine and the one or more aftertreatment subsystems for the program. The controller may prescribe setpoints and constraints for measured variables and positions of actuators according to the program to aid in effecting the optimization and control of the one system.

Abstract: An embodiment of the present invention takes the form of a system that uses exhaust from the combustion turbine engine to heat the fuel gas consumed by a combustion turbine engine. The benefits of the present invention include reducing the need to use a parasitic load to heat the fuel gas.

Abstract: Power plant characteristics are operated in a flexible manner by controlling the power consumption of a CO2 capture and compression system. The impact of CO2 capture and compression on the capacity of a power plant can be minimized to maximize the electric power the plant can deliver to the power grid and the impact of CO2 capture and compression on the average plant efficiency can be reduced, by an operating method and a power plant, in which the power consumption of the CO2 capture system is used to control the net output of the plant.

Abstract: A condenser that restrains fluctuations in the condenser vacuum in a power generating installation. In particular, the condenser has a circulating path through which cooling water flows; a tube nest for condensing steam from a steam turbine with the cooling water; and a discharge path. Additionally, a bypass tube; a control valve for controlling the flow rate of the cooling water supplied from the circulating path to the discharge path; a recirculating path; and a booster pump that controls the flow rate of the cooling water are provided. One of the temperature, the flow rate and both the temperature and the flow rate of the cooling water to flow through the two tube nests is deviated from the temperature and the flow rate of the cooling water on the upstream side of the circulating path using the control valve and booster pump.

Abstract: A power plant frequency response characteristic is implemented by controlling the power consumption of a CO2 capture and compression system. A power reserve is provided for under-frequency events without deloading the plant to part load, by an operating method, in which the power consumption of the CO2 capture system is used to control the net output of the plant.

Abstract: A method of controlling engine exhaust flow through at least one of an exhaust bypass and a thermoelectric device via a bypass valve is provided. The method includes: determining a mass flow of exhaust exiting an engine; determining a desired exhaust pressure based on the mass flow of exhaust; comparing the desired exhaust pressure to a determined exhaust pressure; and determining a bypass valve control value based on the comparing, wherein the bypass valve control value is used to control the bypass valve.

Abstract: The invention concerns a steam circuit process device comprising a reservoir for a liquid working medium; a feed pump for supplying working medium from the reservoir to an evaporator, in which the working medium is evaporated; an expander, to which vaporised working medium is fed by the evaporator, which expands by way of performing mechanical work in the expander; a condenser, which follows the expander and is in fluid connection with the reservoir, whereas the working medium is liquefied in the condenser; The invention is characterised in that the steam circuit process device includes an emptying pump for the working medium which is arranged in a by-pass line between the reservoir and a switchable valve system in fluid communication with at least one further component of the steam circuit process device.

Abstract: Cooled exhaust hood plates are provided in areas of high velocity steam flow within an exhaust steam flow of a steam turbine. Coolant is directed within double walled exhaust hood plates to cool plate surfaces adjacent to the high velocity exhaust steam flow. The cooled exhaust hood plates cool and condense the exhaust steam in proximity. Condensation will occur in low velocity area near the exhaust hood plate to reduce the boundary layer and improve the flow through the hood, improving overall turbine performance.

Abstract: A method of substantially preventing contaminants from entering a condenser adapted for use within a steam generating system. A condenser is provided. Steam or a combination of water and steam is passed into the condenser, the condenser operating in a normal mode if a pressure in a control area is equal to or greater than a predefined pressure and operating in a non-normal mode if the pressure in the control area is less than the predefined pressure. An inert gas is injected into the condenser if a pressure in the control area is less than a holding pressure, the holding pressure being equal to or greater than the predefined pressure.

Abstract: The cooling device is provided with an ECU, a water pump, an engine, a water-cooled exhaust manifold, and a radiator. A first flow rate determination means that determines the flow rate of the cooling water allowed to flow through the water-cooled exhaust manifold based on the intake air flow rate when the operation state of the engine is in a steady state, and a second flow rate determination means that determines the flow rate of the cooling water allowed to flow through the water-cooled exhaust manifold based on the cooling loss when the operation state of the engine is in a transient state are functionally achieved by the ECU.

Abstract: A power generating system including a working fluid circuit. The power generating system includes a condenser system in the working fluid circuit and a condensate polisher circuit. The condenser system receives a working fluid that includes steam or a combination of water and steam and condenses at least a portion of the working fluid into a condensate. The condensate has a temperature above a predetermined upper operating temperature. The condensate polisher circuit is branched off from the working fluid circuit and receives and treats said condensate from the working fluid circuit and returns treated condensate to the working fluid circuit. The condensate polisher circuit includes a heat exchanger that reduces the temperature of the condensate at least to the upper operating temperature and a condensate polisher that removes contaminants from the condensate to bring the condensate to a predetermined purity.

Abstract: A power generating system comprises a condenser and a deaerator apparatus. The condenser condenses a working fluid into a condensate and operates at an internal pressure above ambient pressure during a normal operating mode. The deaerator apparatus uses steam to remove contaminants from the condensate to bring the condensate to a desirable purity. The deaerator apparatus is deactivated during a typical operating state of the power generating system such that the condensate bypasses the deaerator apparatus. The deaerator apparatus is activated during a non-typical operating state of the power generating system such that the condensate passes into the deaerator apparatus wherein contaminants can be removed from the condensate. The typical operating state of the power generating system occurs when the condensate comprises a desirable purity and the non-typical operating state of the power generating system occurs when the condensate comprises an undesirable purity.

Abstract: A method and apparatus reliable, accurate and continuous measurement of air inleakage into the condenser of a steam-electric power plant with convenient monitoring by power plant personnel.

Abstract: A power plant frequency response characteristic is implemented by controlling the power consumption of a CO2 capture and compression system. A power reserve is provided for under-frequency events without deloading the plant to part load, by an operating method, in which the power consumption of the CO2 capture system is used to control the net output of the plant.

Abstract: Provided are high-pressure, medium-pressure, and low-pressure turbines; a boiler to generate steam for driving the turbines; a carbon dioxide recovery unit including an absorber that reduces carbon dioxide in combustion flue gas from the boiler by means of a carbon dioxide absorbent and a regenerator that regenerates an absorbent; a first auxiliary turbine that extracts steam from an inlet of the low-pressure turbine and recovers power by means of the steam thus extracted; a first steam delivery line to supply discharged steam from the first auxiliary turbine to a reboiler of the regenerator as a heat source; and a controller that controls driving of the first auxiliary turbine while keeping pressure of the discharged steam to be supplied to the reboiler within a tolerance range for the reboiler's optimum pressure corresponding to a fluctuation in an operation load of the boiler.

Abstract: A method of controlling engine exhaust flow through at least one of an exhaust bypass and a thermoelectric device via a bypass valve is provided. The method includes: determining a mass flow of exhaust exiting an engine; determining a desired exhaust pressure based on the mass flow of exhaust; comparing the desired exhaust pressure to a determined exhaust pressure; and determining a bypass valve control value based on the comparing, wherein the bypass valve control value is used to control the bypass valve.

Abstract: A process for purifying exhaust gases includes the steps of collecting PMs, forcibly exhausting PMs, and purifying PMs. In the step of purifying PMs, PMs in exhaust gases are collected with a filter. In the step of forcibly exhausting PMs, PMs, which are collected on the filter, are exhausted by blowing a pressurized gas onto the filter, thereby forming PMs-containing gases. In the step of purifying PMs, PMs, which are contained in the PMs-containing gases, are purified by contacting an oxidizing agent with the PMs-containing gases, thereby removing the PMs from the PMs-containing gases by means of oxidation.

Abstract: An exhaust valve assembly includes a flapper valve fixed to a valve shaft where the flapper valve is movable between a closed position, an intermediate position, and an open position. A resilient member biases the flapper valve toward the closed position. An electric actuator actively moves the flapper valve at least from the closed position to the intermediate position. A coupling mechanism couples the valve shaft to an electric actuator shaft and allows the flapper valve to move to the open position in response to exhaust flow sufficient to overcome a biasing force of the resilient member without requiring input from the electric actuator.

Abstract: This invention relates to a speed monitor apparatus for monitoring speed and acceleration of rotating turbine equipment (turbomachinery) and for operating an overspeed trip to shut down the equipment in the event that the speed or acceleration exceed predetermined thresholds. The invention provides a speed monitor module having an output switch comprising a plurality of armature clamped relays such that first armatures form a first electrical path only when both first armatures are open or when both first armatures are closed and second armatures provide a second electrical path when either or both second armatures are open or closed such that the second electrical path is discontinuous when either first armature is stuck in an open or closed position causing either second armature to remain floating between an open and closed position.

Abstract: The present invention relates to a system in which a process of condensing steam or vapor is used for cooling or heating an ambient environment. An increase in the effectiveness of the condensing process is achieved by adjusting the input of steam or vapor into the condenser.

Abstract: In order to evacuate a turbine condenser, air contained in the turbine condenser is suctioned using propellant steam from a starting jet pump. The propellant steam and the air are guided into an auxiliary condenser which is arranged downstream from turbine condenser.

Abstract: Small, rigid electrodes in the form of sharp-pointed rods (“pins”) installed around the periphery of the diffuser at the exhaust of a steam turbine extend into the path of the wet steam flowing out of the turbine and remove electric charge from the steam, whereby turbine back-pressure and turbulence within the exhaust hood are decreased, and the energy conversion efficiency of the power generating unit is increased. In the preferred embodiment these pins are grounded, but pin electrodes isolated from electrical ground with a suitable voltage applied may give better performance in some situations. Similar pins may be installed around the bearing cone facing the turbine exhaust, along the L-stage guide blades, or along the trailing edges of flow guides or baffle plates within the exhaust hood and condenser to remove from the steam charge that may be present in the steam in those places, whereby energy conversion efficiency is likewise increased.

Abstract: The present invention comprises a method and device for deterring the freezing within a condenser by preventing critical pressure differentials from building up between the exhaust steam header and the air ejector systemy. The means for regulating pressure in the air ejector system prevents the pressure difference between the turbine exhaust and the air ejector system from being great enough to carry condensate through a condensing tube into an air ejector system.

Abstract: Small, rigid electrodes in the form of sharp-pointed rods (“pins”) installed around the periphery of the diffuser at the exhaust of a steam turbine extend into the path of the wet steam flowing out of the turbine and remove electric charge from the steam, whereby turbine back-pressure and turbulence within the exhaust hood are decreased, and the energy conversion efficiency of the power generating unit is increased. In the preferred embodiment these pins are grounded, but pin electrodes isolated from electrical ground with a suitable voltage applied may give better performance in some situations. Similar pins may be installed around the bearing cone facing the turbine exhaust, along the L-stage guide blades, or along the trailing edges of flow guides or baffle plates within the exhaust hood and condenser to remove from the steam charge that may be present in the steam in those places, whereby energy conversion efficiency is likewise increased.

Abstract: The invention consists a dual section vessel including a first section being a turbine exhaust steam enclosure and a second section being a condensate water vessel accumulation, both sections being connected by a system of water columns. The system of water columns comprising moderate diffusers for retaining turbine exhaust steam velocity without increasing in pressure, towards impact with cold recirculated condensate water. The recirculated warm condensate water from the condensate water vessel flows through a counter current heat exchanger, and as cold condensate water to dispersion pipes connected to the ends of the diffusers. This complete system is arranged for receiving, compressing and condensing the exhaust steam from the turbine last stage. From the collision location the exhaust steam and condensate water continue to flow as “two phase flow” downward to the “condensate water vessel.

Abstract: A partitioning member for dividing a connecting pipe into at least two exhaust passageways is provided in the connecting pipe, which is attached to an exhaust side of a silencer. A valve mechanism is operable to vary the passageway area of one of the exhaust passageways. With this structure, for example, when an engine is rotating at low revs, exhaust gas is discharged from the exhaust passageway without the valve mechanism, while when the engine is rotating at high revs exhaust gas is simultaneously discharged from the exhaust passageway having no valve mechanism and a passageway provided with the valve mechanism. Therefore, it is possible to reduce exhaust noise when the engine is rotating at low revs.

Abstract: The present invention is directed toward a method and device for increasing the energy efficiency of a power plant. The invention comprises monitoring the power consumption of a power plant subsystem. The subsystem being monitored should be a subsystem that directly influences a measurable condition that is related to generator output. The generator output of the power plant generator is monitored as a function of the measurable condition. The power consumption of the subsystem influencing the measurable condition is compared to generator. The subsystem power consumption can then be adjusted output.

Abstract: A method for capturing working fluid which includes a hazardous component and is discharged from a power generating system, includes directing the discharge to a container. There, the discharged working fluid is combined with a liquid in which the hazardous component is soluble to form a less hazardous mixture.

Abstract: Sufficient negative charge density may be present in the wet steam flowing through the exhaust hood of a steam power generating unit to cause intense electrical discharges which cause severe corrosion of exposed carbon steel members and generate turbulence, decreasing power output. The electric charge density is proportional to current from a charge probe exposed to the flowing steam to ground. Electric charge density can be controlled by adjusting the concentration of ammonia in the steam supply. A small positive charge density will eliminate corrosion and minimize turbulence related to electrical discharges, thereby increasing power generated. The amount of negative charge released can also be decreased by cladding the portions of the flow guides and other carbon steel members located near to the turbine exhaust with stainless steel, or with an appropriately chosen insulating composition.

Abstract: The cooling of a hot fluid is effected using a heat exchanger adapted to receive the hot fluid and liquid coolant for cooling the hot fluid such that the liquid coolant is vaporized. A turbine, having an output shaft connected to a fan, is responsive to vaporized coolant which expands in the turbine for driving the fan to move a mass of air, and produce vaporized coolant. A condenser receives the expanded vaporized coolant and is responsive to air blown by the fan, for condensing the expanded vaporized coolant thereby cooling the same and producing coolant condensate which is then returned to the heat exchanger.

Abstract: A system and method for controlling the operation of a steam condenser in a power plant which includes a steam turbine, the condense having: a steam flow path including a steam inlet connected to receive turbine exhaust steam from the turbine steam outlet, a condensate outlet and a heat exchange region located between the steam inlet and the condensate outlet; a cooling water flow path having an inlet and an outlet and heat exchange elements for conducting cooling water through the heat exchange region, and a non-condensible product removal path having an inlet communicating with the heat exchange region and an outlet located outside of the heat exchange region.

Abstract: A condenser for the water-steam loop of a power plant includes a condensate-filled lower portion. A heating pipe system is disposed in the lower portion and nozzles are disposed on the heating pipe system through which heating condensate or heating steam is forced into the condensate for heating the condensate and thereby expelling dissolved gases from the condensate. A heating valve is connected to the heating pipe system and a proportional regulator is connected to the heating valve for adjusting heating output of the heating pipe system through the quantity of hot condensate or hot steam. A measurement variable converter connected to the proportional regulator acts upon the proportional regulator at least as a function of oxygen content of the condensate and as a function of subcooling of the condensate, the subcooling being equal to the difference between the temperature of the condensate and the temperature of condensation of steam to be condensed.

Abstract: The system and method of the present invention calls for reducing steam from one pressure down to a second pressure. Further, the steam st the one pressure is mixed with the steam at the second pressure. The mixed steam is provided for use in a process. The mixing of the steams is controlled in accordance with the providing of the mixed steam.

Abstract: An improved multi-stage turbine system is provided which includes a high pressure turbine stage assembly and at least one lower pressure turbine stage assembly. Each of these turbine assemblies preferably has an inlet opening for introducing a thermodynamic medium in the form of a vapor and a discharge opening for discharging the thermodynamic medium from the turbine assembly at a reduced temperature and pressure. Each of the turbine assemblies is typically mounted on a rotatable shaft and these shafts may be coaxially aligned. An assembly such as a clutch may be provided for releasably interlocking the shafts. The thermodynamic medium is transported, when operating conditions are suitable, from the discharge opening of the high pressure turbine assembly to the inlet opening of the lower pressure turbine assembly.

Abstract: Disclosed is an apparatus for continuous measurement of the proportion of relatively non-condensable gases in a flow of mixed gases such as geothermal steam. The apparatus is an open system which detects the proportion of relatively non-condensable gases in a sample flow continuously. The sample flow is condensed and supplied in a tube which conditions the sample flow to consist of a series of segments of condensate and segments of uncondensed gases. The sensor senses the relative volume of the condensate and the uncondensed gases. The data processing means receives the output of the sensor and calculates the proportion of non-condensable gases in the flow of mixed gases. In the preferred embodiment, the sensor optically detects the ratio of the volume of the condensate to the volume of uncondensed gases.

Abstract: A system for energy-efficiently operating large capacity cooling pumps in a steam cycle electrical power generating plant which condenses steam using ambient water (e.g., from a lake, cooling tower, or stream) supplied by two or more large electrical motor-driven pumps is disclosed. The system sets reference values for condenser pressure, ambient water temperature, and feedwater flow or electric load, and when conditions change significantly, it cycles on or off one pump, measures and calculates energy efficiency, and depending upon those calculations, either recycles the pump off or on or maintains the status quo and updates the reference values for the plant, and automatically repeats the process upon another significant change of conditions. The system uses a digital computer, sensors, and interface units, for automatically controlling on or off the electric motors of the pumps.

Abstract: An engine which can operate satisfactorily on sources of relatively low heat, such as waste heat given off by steam generating plants, includes a heating tank operably positioned with respect to a source of heat so that fluid within the tank is heated. The fluid in the tank is selected so that its boiling point is below the temperature of the heating tank. In this way the fluid is pressurized in the tank. The pressurized fluid flows to a turbine having a hollow central shaft with hollow vanes extending radially therefrom. The pressurized fluid flowing from the ends of the vanes cause the turbine to rotate. A housing about the turbine collects the fluid expelled from the vanes. The fluid then flows through a conditioning means into a storage tank where it is then introduced back into the heating tank to be recirculated. Electronic circuitry is provided to monitor and control operation of the engine.

Abstract: A Rankine cycle apparatus comprises a circulating pump for circulating a working medium through the apparatus, a gas generator having a tube connected with the outlet side of the circulating pump wherein the working medium flowing in the tube is evaporated, an expander connected with the outlet side of the tube of the gas generator, a condenser having a tube connected between the outlet side of the expander and the inlet side of the circulating pump wherein the working medium flowing the tube is condensed, pressure and temperature sensors for sensing the pressure and temperature of the working medium at the outlet side of the gas generator, and a flow control valve for controlling the rate of flow of the working medium to the gas generator on the basis of the pressure and temperature sensed by the sensors.

Abstract: An arrangement of controls for a vapor compression open cycle industrial process heat pump permits the level of liquid and fluid pressure in a flash tank to be simultaneously and independently monitored and regulated to assure efficient operation of the system and to prevent equipment failure. Liquid level sensing means send a signal to a modulatable valve associated with a liquid discharge pump to maintain the liquid in the flash tank at an optimum level. At the same time, fluid pressure sensing means send a signal to a modulatable inlet throttle valve to regulate fluid pressure in the tank by regulating fluid as required, to maintain tank fluid pressure at the desired level.

Abstract: Condensation system for use in a power plant. The condensate system includes side stream condenser defining therein first and second hot wells. Condensate is delivered from the first to second hot well through a condensate feed line. Condensate is introduced from the condensate feed line into a tank through a first spill-over line. Condensate is supplied from the second hot well to the power plant through a main condensate feed line. Condensate is introduced from the main condensate feed line into the tank through a second spill-over line. Actuator is operative in response to signal from a level detector detecting level of condensate in the first hot well, to regulate opening degree of a supplementary feed valve in the supplementary feed line, to close one of first and second spill-over valves in the first and second spill-over lines, respectively, and to open the other spill-over valve.

Abstract: Spent steam from a steam driven electric generating power plant is condensed by heat rejection to a refrigerant in a closed loop. The closed refrigerant loop contains an expander and a compressor, and a heat exchanger in a cooling tower. The compressor and expander are integrated so that (1) in an upper cooling cycle at the upper end of the ambient or air temperature range, only the compressor is operated within its operating range, (2) in a lower cooling cycle at the lower end of the ambient or air temperature range, only the expander is operated and (3) in a middle cooling cycle at the middle range of the ambient or air temperatures, when the turn-down of either the compressor or the expander is a limiting factor, both of them are operated.