Showing papers on "Thermal expansion valve published in 2002"

Apparatus and method for extracting potable water from atmosphere

Abstract: Apparatus and method for extracting potable drinking water from moisture-laden atmospheric air through the use of a refrigeration system. A compact housing contains a compressor, an evaporator unit, fan unit, condenser unit, and a reservoir which may contain a secondary evaporator unit and condenser unit. The fan pulls a stream of atmospheric air through a filter and through the evaporator to clean and cool the air and exhausts cooled air through the condenser. The water is collected as condensation by the evaporator and directed to the reservoir through a filter system and a water seal. The reservoir may have separate compartments for holding cool or warm water. The secondary evaporator is submersed in the cool water compartment for cooling the water collected in the reservoir and the secondary condenser is submersed in the warm water compartment for heating the collected water. Operation of the system is controlled by a control module which may also contain a microprocessor for assuring maximum condensation and a removable I.C. program module to alter the operation for specific conditions. A humidistat may also be provided to maximize efficiency of atmospheric condensation throughout various times of day or night and in various climates.

Modeling and experimental evaluation of an automotive air conditioning system with a variable capacity compressor

Abstract: A steady state computer simulation model has been developed for refrigeration circuits of automobile air conditioning systems. The simulation model includes a variable capacity compressor and a thermostatic expansion valve in addition to the evaporator and micro channel parallel flow condenser. An experimental bench made up of original components from the air conditioning system of a compact passenger vehicle has been developed in order to check results from the model. The refrigeration circuit was equipped with a variable capacity compressor run by an electric motor controlled by a frequency converter. Effects on system performance of such operational parameters as compressor speed, return air in the evaporator and condensing air temperatures have been experimentally evaluated and simulated by means of developed model. Model results deviate from the experimentally obtained within a 20% range though most of them are within a 10% range. Effects of the refrigerant inventory have also been experimentally evaluated with results showing no effects on system performance over a wide range of refrigerant charges.

Air conditioning systems

Abstract: An air conditioning system includes a refrigerant circuit. The refrigerant circuit includes a compressor for receiving a refrigerant gas and for compressing the refrigerant gas, and a condenser for condensing a portion of the compressed refrigerant gas into a liquid refrigerant. The refrigerant circuit also includes an expansion valve for reducing a pressure of the condensed liquid refrigerant, and an evaporator for evaporating the condensed liquid refrigerant. Moreover, the compressor is driven by an electric motor which controls a rotational speed of the compressor via an inverter, and a temperature of the inverter is decreased by the refrigerant circuit. The system also includes an electric circuit for determining whether a temperature of the inverter is greater than a first predetermined temperature, and an electric circuit for controlling a rotational speed of the compressor. Specifically, when the temperature of the inverter is greater than the first predetermined temperature, the electric circuit decreases the rotational speed of the compressor.

Refrigeration cycle system

Abstract: PROBLEM TO BE SOLVED: To provide a refrigeration cycle combined system constituted by combining a compression refrigeration cycle and an absorption refrigeration cycle using an ejector. SOLUTION: The refrigeration cycle using the ejector comprises the ejector 10, a vapor generator 11 for feeding driving pressure vapor to the ejector 10, a condenser 12, an expansion valve 14a and an evaporator 14. Returning refrigerant vapor from the evaporator 14 is sucked by pressure refrigerant introduced into the ejector 10 and sent to the vapor generator side.

Apparatus and method for actively cooling instrumentation in a high temperature environment

Abstract: An apparatus and method are disclosed for actively cooling instrumentation, such as electronic circuits, in a downhole tool. This apparatus includes a compressor, condenser and expansion valve connected in circuit to an evaporator or heat exchanger. The evaporator/heat exchanger includes an inner container positioned about the instrumentation, and an outer chamber positioned about the inner container. A cooling fluid absorbs heat from the instrumentation as it passes through the inner container. The fluid then passes into the outer container where it may absorb heat from the wellbore. The heated fluid is then pressurized via the compressor, condensed into liquid via the condenser and selectively released back into the internal container upon cooling via the expansion valve. The fluid continuously circulates through the system whereby the instrumentation is insulated from heat and/or cooled.

Apparatus and method for controlling the temperature of an electronic device under test

Abstract: An apparatus for controlling the temperature of an electronic device under test includes a thermal head having a temperature controlled surface for making thermal contact with the electronic device. The thermal head defines a flow channel for passage of a refrigerant fluid so as to cause transfer of thermal energy between the electronic device and the thermal head. A refrigeration system is connected in fluid communication with the flow channel of the thermal head to supply refrigerant fluid thereto. The refrigeration system includes a metering valve operative to regulate introduction of the refrigerant fluid into the thermal head. A controller is operative to control the metering valve for maintaining a predetermined temperature at the temperature controlled surface.

Orientation-independent thermosyphon heat spreader

Abstract: Device for enhancing cooling of electronic circuit components that is substantially or fully independent of orientation. A thin profile thermosyphon heat spreader (20) mounted to an electronics package comprises a central evaporator (28) in hydraulic communication with a peripheral condenser (30), both at least partially filled with liquid coolant. A very high effective thermal conductivity results. Performance is optimized by keeping the evaporator (28) substantially full at all orientations while leaving a void for accumulation of vapor in the condenser (30). A cover plate (24) and a parallel base plate (22) of generally similar dimension form the evaporator (28) and condenser (30). Optionally, an opening in the base plate (22) is sealed against the electronics package and places the heat-dissipating component in direct contact with the liquid coolant. Alternatively, the base plate (22) may be formed with the electronics package from a single piece of material. A boiling enhancement structure (34)is provided in the evaporator (30) to encourage vapor bubble nucleation.

Electronic module including a cooling substrate and related methods

Abstract: An electronic module (20) includes a cooling substrate (21a), an electronic device (22) mounted thereon, and a heat sink (23) adjacent the cooling substrate (21a). More particularly, the cooling substrate (21a) may have an evaporator chamber (25) adjacent the electronic device (22), at least one condenser chamber (26) adjacent the heat sink (23), and at least one cooling fluid passageway (27) connecting the evaporator chamber (25) in fluid communication with the at least one condenser chamber (26). Furthermore, an evaporator thermal transfer body (28) may be connected in thermal communication between the evaporator chamber (25) and the electronic device (22). Additionally, at least one condenser thermal transfer body (36) may be connected in thermal communication between the at least one condenser chamber (26) and the heat sink (23). The evaporator thermal transfer body (28) and the at least one condenser thermal transfer body (36) preferably each have a higher thermal conductivity than adjacent cooling substrate portions.

Experimental investigation of a minimum stable superheat control system of an evaporator.

Abstract: In this paper, the minimum stable superheat of an evaporator has been studied with respect to the refrigerant flow and heat transfer. The change of heat transfer mechanism of refrigerant in the superheat regulation process has been unveiled. It was neglected in the past.

Hybrid temperature control system

Abstract: A method of operating a hybrid temperature control system. The method provides an evaporator, which has a discharge line, a supply line, and a evaporator coil. The evaporator coil is in fluid communication with the discharge line and the supply line. The method also provides a microprocessor, which regulates a supply of a heat absorbing fluid to the evaporator. The method further couples a sensor module to the microprocessor. The sensor module is near the evaporator, senses a temperature of a gas exiting the evaporator, and sends a temperature to the microprocessor. The method also turns off the supply of the heat absorbing fluid to the evaporator when the microprocessor determines that the temperature of the gas exiting the evaporator reaches a predetermined temperature.

Variable capacity refrigeration system with a single-frequency compressor

Abstract: A variable capacity refrigeration system which does not require a costly inverter compressor and does not exhibit low energy efficiency at high capacity. The system employs a constant speed compressor that operates continuously when the system is energized, irrespective of the heat load, and a refrigerant bypass path including a secondary expansion device, a heat exchanger, and a flow control device which is operable to permit a portion of the refrigerant exiting from the condenser to flow through the bypass path to an inlet of the compressor when the heat load is below a predetermined threshold, whereby the heat exchanger operates as a secondary evaporator, and to prevent refrigerant exiting from the condenser from flowing through the bypass path to the compressor inlet when the heat load is not below the predetermined threshold. In one embodiment, the flow control device is further operable to permit a portion of the refrigerant exiting from the compressor to flow through the bypass path to the primary evaporator through the primary expansion device when the heat load is not below the predetermined threshold, whereby the heat exchanger operates as a secondary condenser. In several embodiments, a pressure differential is maintained between the refrigerant in the heat exchanger and the evaporator. The pressure differential is accommodated by a vacuum generating device such as a vortex generator, a venturi or the like, or by a flow restrictor such as a capillary tube. In several embodiments, the heat exchanger is thermally coupled to the compressor to remove heat from the refrigerant as it flows through the compressor.

Chilling unit with “free-cooling”, designed to operate also with variable flow rate; system and process

Abstract: A unit comprises a refrigerating circuit ( 30 ), at least part of a primary circuit ( 110 ), and connections ( 151, 152 ) for a user's circuit ( 120 ). The refrigerating circuit comprises an evaporator (E), a compressor ( 31 ), a condenser battery (C), and an expansion valve ( 34 ), and connection lines. The primary circuit extends through the evaporator and through an air-cooled “free-cooling” battery (FC). To allow a variable flow through the free-cooling battery, though maintaining the flow rate constant through the evaporator, the primary circuit ( 110 ) comprises a bypass line ( 140 ) extending between an outlet line from the evaporator and an inlet line to the evaporator, and a storage tank (A) on said bypass line.

An experimental and numerical study of hunting in thermostatic-expansion-valve-controlled evaporators

Abstract: The dynamic behaviour of a thermostatic-expansion-valve (TEV)-controlled dry-evaporator is studied experimentally and numerically. Although the linear model of the TEV together with the distributed model of the evaporator is able to predict the stable dynamic response of the system adequately, it fails to reproduce the hunting behaviour that is observed under certain operating conditions. A scrutiny of the experimental data reveals the possible existence of hysteresis in the system. The distributed model including the experimentally determined input-output characteristics of the TEV is able to reproduce the main features of the hunting oscillations well. The amplitude and frequency of these oscillations depend on the static superheat setting, the heat load of the evaporator and the time constant of the TEV bulb.

Method and apparatus for controlling the removal of heat from the condenser in a refrigeration system

Abstract: This invention increases efficiency of a refrigeration system (10) by maximizing the cooling of the condenser (14) and reducing unnecessary work done by the compressor (12). In air cooled systems it will also increase the stability of the fans (16) by reducing fan cycling. The fan controller (24) will utilize an algorithm that will consider the following inputs: oil pressure, compressor suction pressure, expansion valve position, compressor loading, last compressor loading change, and current fan stage. The algorithm uses fuzzy logic to characterize the inputs and generates an output that controls the system cooling fans (16).

Dehumidifier for use in mass transit vehicle

Abstract: An evaporator unit for use in the air conditioning system of a mass transit vehicle that includes a housing mounted inside the air conditioned section of the vehicle having a return air inlet connected to a supply air outlet by a flow passage. The evaporator coil of the air conditioner is mounted in the flow passage to cool the air moving through the passage. A heater coil is mounted behind the evaporator coil to selectively heat the air moving through the passage. A dehumidifying coil is mounted in front of the evaporator coil that utilizes ambient air to dehumidify the indoor air when the ambient air temperature is at a temperature below that at which the air conditioner cannot reliably operate.

Advanced refrigeration system

Abstract: A transportation refrigeration system operable in a cooling mode, a defrost mode, and a heating mode to condition air in an air-conditioned space. The system comprises a refrigeration circuit fluidly connecting a compressor, a condenser, a tank, and an evaporator. The evaporator is in thermal communication with the air-conditioned space. A heating circuit fluidly connects the compressor, the tank, the evaporator, and a heater. A defrost circuit fluidly connects the compressor, the tank, the evaporator, and the heater. The tank has a base and the first opening is spaced a first distance above the base and the third opening is spaced a second greater distance above the base.

Air-conditioning unit with additional heat transfer unit in the refrigerant circuit

Abstract: The invention relates to an air-conditioning unit (10) for a motor vehicle with a heating heat transfer unit (28), connected to a coolant circuit (42) on an internal combustion engine, with a pre-arranged evaporator (22), viewed in the direction of flow of a fan (36). A compressor (12) in a refrigerant circuit (32) supplies a refrigerant through a gas cooler (16) and an expansion valve (20) during a cooling operation and pumps said refrigerant to the evaporator (22) via the expansion valve (20), by by-passing the gas cooler (16) during a heating operation. A coupled heat exchanger (30) is provide between the cooling fluid circuit (42) and the refrigerant circuit (32). According to the invention, the coupled heat exchanger (30) is arranged in the refrigerant circuit (32) on the pressure side of the compressor (12) before the gas cooler (16), a first by-pass line (80) is provided parallel to the gas cooler (16) and the flow through the gas cooler (16) and the first by-pass line (80) is controlled by a switching valve (52) in the first by-pass line (80) and a switching valve (48, 50) at each of the input and output from the gas cooler (16), depending on operating parameters and a heat transfer unit (14) for a medium in a unit in the refrigerant circuit (32) is connected behind an expansion valve (20 or 38) and serves as heat source in heating operation.

Installation used to obtain salt-free sea water at a low temperature with continuous operation and enthalpy recovery

Abstract: The invention relates to a sea water desalination installation that employs an evaporation-condensation system which operates continuously at a low temperature and which enables the recovery of energy released. The inventive installation comprises a cylindrical evaporator having a large evaporation surface and a concentric condenser with a large surface area. Sea water is used to cool the condenser and said water is subsequently sent to the evaporator. A static high-pressure ventilator is used to: (i) drive the vapour/air in a closed circuit between the evaporator and the condenser and (ii), using a calibrated nozzle, create a pressure gradient that is equivalent to the pressure of the saturated vapour at working temperature between said two zones. The aforementioned evaporator and condenser are thermally insulated in relation to one another and to the external environment.

Air fractionation in columns producing liquid and gaseous products, exchanges heat with circuit containing recirculated cryogenic liquid

Abstract: Air is introduced into a fractionation system including one or more columns (3, 4). A liquefied product stream (11, 15) is extracted. This is introduced into an evaporator (17), where it is evaporated by indirect heat exchange, and a gaseous product (18) is withdrawn. Fluid (19) is recirculated around a closed circuit (23, 26-31) in which it is compressed (20), liquefied in the evaporator, and returned again to the compressor. The liquefied recirculated fluid (23) is evaporated downstream of the compressor by indirect heat exchange with a condensing, heating fluid (34, 36) in a condensing evaporator (25). Preferred features: The recirculated fluid is an air component or a mixture of them, preferably nitrogen or air. Heating fluid (37) condensed in the condensing evaporator is introduced into one or more the fractionating columns. Heating fluid (34, 36) is extracted from one or more of the separation columns before its introduction into the condensing evaporator. Some of the compressed fluid (22) is expanded to produce power (33) and returned (29, 31, 19) to the compressor. The condensing evaporator is operated as a falling film evaporator.

Condensation laundry dryer has heat pump device having evaporator incorporated in heat exchanger of warm air process loop

Abstract: The laundry dryer has a closed process loop (2) in which warm air is supplied to the drying chamber (1) via an air inlet and extracted via an air outlet, supplying it to a heat exchanger (6) for moisture removal, before re-heating and recirculation via a fan (3). An evaporator (9) and a condenser (11) for the heat pump circuit are contained in the warm air process loop, the evaporator incorporated in the heat exchanger and the condenser in the heating device, the evaporator having 2 parallel heat exchange surfaces (14,15), with separate regulation of the cooling medium flow fed to each.

Heat transferring device having adiabatic unit

Abstract: A heat transferring device having an adiabatic unit is provided. The heat transferring device includes a lower plate including an evaporator which contacts a heating element and allows a liquid refrigerant to absorb heat transferred from the heating element to thus evaporate, a condenser in which gas flowing from the evaporator is condensed, a gas passage through which the gas flowing from the evaporator into condenser, a liquid refrigerant passage through which the liquid refrigerant flows from the condenser into the evaporator and which includes a portion used as a channel region bordering the evaporator, and an adiabatic unit provided between the liquid refrigerant passage and the gas passage so that elements hindering the flow of the liquid refrigerant can be prevented from being introduced from the gas passage into the liquid refrigerant passage; and an upper plate which contacts some members of the lower plate including the adiabatic unit.

Design considerations for a second-generation CO2-expander.

Abstract: If one replaces the throttle valve in a transcritical CO2 refrigeration cycle by a work extracting expander, the COP of the cycle can theoretically be improved by about 60%. In the past few years, in the authors' laboratory, a first-generation expander for this purpose was tested and a COP improvement of about 30% was achieved. Apparently there is room for further improvement. In the first-generation machine, the expander could be operated only in the so-called full-pressure mode. The authors present design considerations for a second-generation expander-compressor, which should overcome this drawback.

Enhanced cooling system

Abstract: An air conditioning system is disclosed which takes advantage of low ambient temperature conditions so as to activate a refrigerant flow that bypasses the compressor. The activation of the refrigerant flow is achieved by the intelligent control of a pump positioned between the outlet of the condenser and the inlet of an expansion device upstream of the evaporator. The refrigerant flow produced by the pump does not require any particular positioning of the condenser and evaporator components with respect to each other. The evaporator preferably absorbs heat from water circulating in a secondary loop which is used to remove heat from a building by one or more fan coil units.

Humidity control and efficiency enhancement in vapor compression system

Abstract: A vapor compression system includes a vapor compression circuit including a compressor, a condenser, an expansion device and an evaporator communicated along refrigerant conveying lines; an evaporator air reheat circuit communicated with the vapor compression circuit for reheating air from the evaporator; and a refrigerant subcooling circuit communicated with the vapor compression circuit for subcooling refrigerant from the condenser, whereby humidity in the air from the evaporator can be controlled while system efficiency is maintained by the refrigerant subcooling circuit. The system further enhances system unloading capability, and part-load operation and reliability are also enhanced.

A Dynamic Model Of A Vapor Compression Liquid Chiller

Abstract: Dynamic models of vapor compression systems are important tools for HVAC engineers in the development and evaluation feedback control and fault detection and diagnostic (FDD) algorithms. Significant literature exists on dynamic models of vapor compression systems. Much of it is restricted to air-to-air systems and few papers deal with liquid chillers. Most of existing liquid chiller models reviewed were found to use lumped capacitances for the heat exchangers, and black-box models for the compressor. Also, little or no information has been presented on execution speeds. The current work was undertaken to meet the requirement of a dynamic model of a vapor compression centrifugal chiller based on first-principles that runs at speeds close to real-time. A dynamic centrifugal water chiller model is developed and validated using experimental data. The shell-and-tube heat exchangers are modeled using a finite-volume formulation. The centrifugal compressor is developed from a combination of a simple physical model and a quasi-steady state model. Inlet guide vane capacity control is incorporated. A first principles thermostatic expansion valve is used. The model is validated using data from a 90ton centrifugal chiller test stand, operating with R134a. Model performance during start-up and a typical load change transient is presented. The model was implemented in C++, and allows for flexibility in application to other systems of similar configuration. Also, the model is modular, allowing component models to be replaced. Modelspeed to real-time ratios in the range 1.0-1.2 are achieved on a Pentium 4 1.8GHz/512MB computer. NOMENCLATURE Symbols A heat transfer area . m mass-flow rate . V volumetric flow rate a0...a4 Constants M Mass v specific volume c0...c4 regression coefficients Nu Nusselt number W specific polytropic work Cp specific heat P Pressure, power y valve lift C Constants Pr Prandtl number α heat transfer coefficient D tube diameter . Q heat transfer rate γ control factor f friction factor Re Reynolds number η polytropic efficiency g Accn. due to gravity T temperature (C) μ dynamic viscosity h specific enthalpy u specific internal energy ρ density k thermal conductivity, spring compliance V node volume (m ) . " r Q refrigerant heat flux Subscripts 1 Evap exit 2 Comp exit 3 Cond exit 4 Evap inlet b Bulb c Cond e Evap i i node t Tube we Evap water cc Comp cooling em Electro-mech in Inlet, inner v Vapor, valve wc Cond water INTRODUCTION Dynamic models are crucial tools for the controls engineer in developing efficient control algorithms. Dynamic performance modeling of vapor compression systems has been of interest for well over 20 years, beginning with Dhar and Soedel [1979]. In preparation for this model development exercise, an extensive literature survey was carried out and is reported in a separate document (Bendapudi and Braun [2002]). Papers related to liquid chiller models include Sami et al [1987], Svensson [1999], Wang and Wang [2000], Browne and Bansal [2000] and Grace and Tassou [2000]. None of these models is comprehensive in that they either do not consider centrifugal compressors or they use simplified heat exchanger models that cannot adequately model large and small scale transients. Sami’s model used a hermetically sealed reciprocating compressor, while Browne’s dealt with screw compressors. Svensson’s work presented only transients triggered by feedback control. Wang’s model, which does characterize a centrifugal liquid chiller model, utilizes very simple heat exchanger models. Grace and Tassou modeled a reciprocating compressor with a shell-and-tube evaporator that operated with refrigerant flowing inside the tubes. The heat exchangers were modeled as done by MacArthur and Grald [1987]. Browne and Bansal [1998], in their compilation work on issues related to modeling of vapor compression liquid chillers, highlight the need for a liquid chiller model that incorporates detailed heat exchangers. To summarize, it was found that no publicly available system models existed that could predict the complete dynamic performance of vapor compression centrifugal liquid chillers despite such systems being among the more popular configurations in the field. These observations provided the motivation for defining the modeling objectives as follows: Develop a transient model of a vapor compression centrifugal liquid chiller system that: • is based on first principles wherever available information permits • can capture start-up transients, as well as transients caused by feedback control • can execute close to real-time, if not faster and • can be used to study (in the future) the impact of common faults that occur in such systems TEST STAND DESCRIPTION The test stand used for the validation of the model is a 90-ton water chiller charged with R134a. The refrigeration system itself consists of a centrifugal compressor with variable inlet guide-vanes for capacity control. The heat exchangers are of shell and tube construction, with two-water passes and one refrigerant pass. The expansion valve is a cascaded device consisting of a main valve driven by a pilot valve. The compressor is powered by an electric motor. The motor and transmission are cooled by the refrigerant through a bleed line tapped off of the liquid line, as shown in Fig. 1. This refrigerant returns to the evaporator inlet. The load on the chiller system is controlled by an arrangement of heat exchangers that simulate the building load, as shown in the Fig. 2. For clarity, the pumps and valves that control the water flow rates are not shown. The load on the system can be varied by altering the temperatures of the water entering the evaporator and condenser, i.e., varying the operating conditions of these peripheral heat exchangers. An exhaustive description of the test stand and instrumentation is provided in Comstock [1999]. Fig. 1 Refrigerant flow paths Fig. 2 Water flow paths Condenser