Showing papers on "Thermal expansion valve published in 1980"

Electronically commutated motor systems and control therefor

Abstract: Electronically commutated motor and control arrangements particularly adapted for use with refrigeration systems and methods of operating refrigeration systems are disclosed. In one form, a fan control means is provided for responding to temperature of a compartment being cooled by a refrigeration system; comparing the compartment temperature with a desired temperature; and varying the speed of an evaporator fan, thereby varying the movement of refrigerated air across an evaporator and into the compartment. A regulating circuit is provided for maintaining the evaporator at a reference temperature by controlling the output signal of an alternator which supplies energization power to winding stages of a brushless DC motor. By varying the energization level of the winding stages, a compressor, which is coupled to the motor, is caused to vary the flow rate of refrigerant through the evaporator so as to maintain the evaporator at the reference temperature. The regulating circuit includes means for responding to a signal from the fan control means, which is indicative of the fan speed and relative compartment cooling demand, for changing the reference temperature for the evaporator thereby to cause variance in the temperature of air moved about the evaporator by the fan for controlling temperature within the compartment. The regulating circuit also includes: means for limiting and controlling motor winding current to a maximum value; means for limiting motor speed to a predetermined low value; means for limiting and controlling motor speed to a maximum high value; means for assuring a minimum energization level for the motor winding stages; means for limiting the energization level of the winding stages to a maximum voltage value; and means for inhibiting motor operation if the evaporator temperature is less than a predetermined low temperature value.

Hunting of Evaporators Controlled by a Thermostatic Expansion Valve

Abstract: Evaporators controlled by a thermostatic expansion valve can exhibit an undesirable oscillating behavior, known as hunting. The equations describing the hunting can be characterized by an open-loop transfer function, the coefficients of which are the physical parameters of a refrigeration system. Several known experimental facts are explained theoretically by means of this transfer function, which also provides a starting point for finding new methods to improve the behavior. A particular improvement was verified experimentally.

Condition responsive liquid line valve for refrigeration appliance

Abstract: An energy efficient refrigeration system having a valve in series with a fixed flow restrictor between the condenser and evaporator of the system. The valve is controlled to permit fluid flow whenever the compressor is running, and when the compressor is not running, only in the event the pressure at the outlet of the compressor is above a preselected pressure. The preselected pressure is a high pressure, such as would prevent starting of the compressor, which, in the illustrated embodiment, is a rotary compressor. The pressure sensing structure, in the illustrated embodiment, utilizes an analog of the pressure of the liquid refrigerant within the condenser and, more specifically, utilizes a temperature condition which corresponds to the liquid pressure therein. Alternatively, the temperature sensing may be of the condenser or of the ambient space in which the condenser is housed. The control valve and associated control circuit are arranged to provide a fail-safe function and assure that the valve is open whenever the compressor is operating.

Vapor-jet heat pump

Abstract: A heat pump for use in heating residential, commercial or industrial buildings, industrial and agricultural processes and heating of water to moderate temperatures such as may be required in swimming pools or as a water pre-heater for any other use. The system includes a fuel consuming refrigerant boiler for producing a refrigerant in vaporized form at relatively high pressure, the output of the boiler being connected to a superheater and then to the primary jet of an ejector-type compressor. An evaporator unit exposed to ambient temperatures has its output line connected to an inlet of the ejector such that as the high pressure gaseous refrigerant flows through the nozzle of the ejector, a low pressure is created and the refrigerant from the evaporator is also caused to flow through the ejector compressor to a condenser where the refrigerant is allowed to give up its heat. The condenser is coupled in circuit with a receiver which holds liquid refrigerant and delivers same to the boiler and evaporator, all under control of fluid level or pressure sensitive switches governing the operation of a liquid refrigerant pumping means.

Combination reversing valve and expansion device for a reversible refrigeration circuit

Abstract: Apparatus is disclosed for serving as both a reversing valve and an expansion device in a refrigeration circuit A valve gate having passageways to direct refrigerant between the indoor and the outdoor heat exchangers to effect the function of a reversing valve is disclosed In addition, the valve gate has multiple flow restriction devices which are selectively incorporated within a refrigeration circuit between the indoor heat exchanger and the outdoor heat exchanger to effect the appropriate amount of flow restriction dependent upon the mode of operation of the unit These two functions may be incorporated into a single valve or they may be separated such that the separate functions are performed by separate valves A cylindrical valve gate and multiple passageways for connecting the appropriate lines in a refrigeration circuit are described The valve is rotated by a combination of an electromagnet spaced about the valve gate and a permanent magnet located within the valve gate

Head pressure control including means for sensing condition of refrigerant

Abstract: A sensing device detects "flashing" in a refrigerant liquid line, upstream from the expansion valves of the evaporators of a refrigeration system In response, a valve opens in a line extending between the compressor discharge line and a receiver, to bypass discharge vapor into the receiver, thus raising the head pressure to an extent sufficient to satisfy the requirement for a steady liquid refrigerant flow at the expansion valve The head pressure is raised only to the minimal extent necessary to satisfy this requirement Disclosed is a sensor of the type incorporating a sight glass in the path of a beam extending between photoelectric cells, though other sensing devices of an equivalent nature can be used The invention can comprise a single sensing device in the liquid line extending to one or more evaporators connected in parallel Alternatively, one may utilize separate sensing devices, one for each of several evaporators connected in parallel, with each sensing device having the capability of operating the valve, thus to assure a minimal but sufficient head pressure within the liquid line sufficient to maintain a liquid refrigerant seal at the expansion valve where flashing has been detected by its associated sensor

Method and apparatus for integrating components of a refrigeration system

Abstract: A flash subcooler is provided to meter a portion of the refrigerant flowing from the condenser to the evaporator to an intermediate heat exchanger to subcool refrigerant flowing from the condenser to the evaporator. This diverted refrigerant is flashed to provide subcooling and is then redirected to the compressor as is the flow of refrigerant from the evaporator. Both the refrigeration system and and subassemblies for accomplishing the above are disclosed as well as methods of operation thereof.

A cooling system

Abstract: Air conditioning apparatus (3) has a compressor (6), a condensor (7), an evaporator (8), an expansion valve (9), a blower (10) and a pump (11). Cooling water from outdoor cooling tower 4 is passed to the condensor (7). Air circulating in computer room (1) passes evaporator (8) of the air conditioning apparatus (3) to be cooled. A cold water switching valve (12) is provided for diverting cooling water supplied by tower (4) from condensor (7) to a cold water coil (13). When the outside temperature is low enough to give sufficiently cold cooling water, valve (12) is operated to divert cooling water from the condensor (7) to the cold water coil (13), the compressor (6) is switched off and air circulating in the computer room (1) is cooled by cold water coil (13), instead of evaporator (8).

Air conditioning system

Abstract: In an air conditioning system including a compressor, a condenser for condensing a refrigerant through heat exchange with outdoor air, an expansion valve, an evaporator for evaporating the refrigerant through heat exchange with air to be conditioned, and piping connecting these parts together to form a closed main circuit for the refrigerant, there is provided a bypass circuit connecting a point in the main circuit between the condenser and expansion valve to a point in the main circuit between the evaporator and compressor. The bypass circuit includes a relief valve adapted to open when the internal pressure of the condenser in the main circuit exceeds a predetermined level, pressure reducing means, and a heat exchanger for causing heat exchange to take place directly between the refrigerant in a high pressure section of the main circuit and the refrigerant having its pressure reduced by the pressure reducing means whereby an inordinate rise in the pressure of the refrigerant in the high pressure section of the main circuit due to a lowering in the capability of the condenser can be prevented.

Mechanical vapor recompression evaporators

Abstract: The present invention relates to a process for providing make-up heat in a mechanical vapour recompression evaporator (1, 8, 9). It includes using the evaporation vapour created in another evaporator (5) called make-up evaporator. The invention finds particular application in the dairy industry.

Self-contained heating and cooling apparatus

Abstract: A reverse air cycle type heat pump is provided that utilizes unidirection refrigerant flow wherein the condenser and evaporator retain their functions, but the air directed across them is redirected for different operations. The air cycle type heat pump is further provided with a secondary defrost circuit including valves which permit refrigerant flow to by-pass the compressor and the expansion device only when compressor operation terminates and the system pressure differential is equalized. This defrost circuit causes the relatively warm refrigerant in gaseous phase in the condenser to displace the relatively cold refrigerant in liquid phase in the evaporator with the flow continuing until the defrost system is completed.

Air source heat pump with displacement doubling through multiple slide rotary screw compressor/expander unit

Abstract: A closed loop refrigeration system such as an air source heat pump includes a hermetic screw compressor and a helical screw rotary expander connected to an electric induction drive motor. The closed loop refrigeration circuit permits an air source evaporator to constitute a heat source for supplying vaporized refrigerant to the compressor and expander, while both are mechanically coupled to the electric induction drive motor and with both driven as compression units. The air source evaporator feeds to slide valve controlled inlet ports of both the compressor and expander. Compressed vapor from both units passes to condenser coil(s) such as heating condensers to increase the system capacity under this mode.

Non-reverse hot gas defrost system

Abstract: A method and apparatus utilizing a hot gas defrost system wherein superheated gas from the system compressor is conducted into a heat exchanger mounted within an accumulator for supplying heat to vaporize liquid refrigerant received from the evaporator. After the gas passes through the heat exchanger it is conducted to the condenser where it is condensed to a liquid and then routed to the evaporator. In the evaporator or frost accumulating coil the liquid refrigerant is subcooled, supplying heat to melt the ice formed on the evaporator surfaces and the liquid is thereafter conducted to the accumulator where the heat supplied from the heat exchanger acts to vaporize the fluid. The vaporized refrigerant is then recycled to the compressor to complete the system.

Air conditioner/heat pump conversion apparatus

Abstract: Heat pump/air conditioning converter apparatus for directing a refrigerant from a compressor to a first heat exchanger located within a building and a second heat exchanger located outside the building for selectively cooling and heating the first heat exchanger. The apparatus has a housing within which a reversing valve, a liquid refrigerant flow control valve system, an expansion valve and an accumulator tank is incorporated. The housing has a number of cavities for receiving the various components of the valves and tank, and a number of passageways for directing the refrigerant to the components to minimize the number of external connections. The reversing valve incorporates an axially slideable rod having a large main piston positioned centrally thereon and a pair of smaller valve opening/closing piston members at each end, one end controlling the hot high pressure gaseous refrigerant and the other end controlling the low pressure relatively cool gaseous refrigerant. The liquid refrigerant flow control valve includes a ball valve moved by high pressure fluid and a pair of check valves in the low pressure liquid path from the expansion valve. The accumulator is disposed between the gaseous portion of the apparatus and the liquid portion of the apparatus and includes accessible filter elements in the liquid and the gaseous path.

Thermostatic expansion valve with remote adjustment

Abstract: A thermostatic expansion valve for use in a refrigeration system (eg, a refrigerated display case) in which the superheat range of the valve may be conveniently adjusted from a location remote from the valve

Desuperheater control system in a refrigeration apparatus

Abstract: A desuperheater control system for use in a refrigeration apparatus includes a thermostatic expansion valve which responds to the temperature and pressure at the outlet of a desuperheater for bypassing refrigerant flow from the condenser back to the suction side of the compressor. A pressure chamber is connected to the outlet of the expansion valve to sense the pressure therein. A water regulating valve is responsive to the pressure in the pressure chamber for regulating the water flow through the desuperheater so that the superheated refrigerant gas from the compressor is cooled to a pre-selected temperature having a minimum superheat.

Refrigeration system and novel heat exchanger therefor

Abstract: A refrigeration system for cooling and drying hot moist compressed air comprises sub-cooling the liquid refrigerant from the condenser to eliminate all flash gas and render the entire evaporator effective for refrigeration purposes. The heat exchangers for the evaporator and for sub-cooling the liquid refrigerant are of a novel construction comprising a one-piece finned copper inner cylinder with the routed fin enclosed inside of an annular copper shell in which a 0.020-inch clearance exists between the annular copper shell and the fins to allow passage of a stream of air which causes the laminar flow around the routed fin construction to be agitated by eddy diffusion. The use of the novel heat exchanger in the refrigeration system along with the step of sub-cooling the liquid refrigerant produces a gain in refrigeration effect of about 23% to 30% without an increase requirement for either power or energy.

Motor vehicle air conditioning system - with shunt line to heat exchanger to heat vehicle

Abstract: The air conditioning system has a compressor which supplies coolant to a condenser, an expansion valve and a vaporising chamber to cool the inside of the vehicle. A simple shunt control enables compressed fluid to be passed directly to the condenser to force warm fluid to the heat exchanger and heat the inside of the vehicle. The compressor circuit is used for both heating and cooling and provides a low cost air conditioning system for all the year round operation. No additional booster heater is required.

Regulating circuit for the valve of a refrigeration plant

Abstract: The invention relates to a valve assembly for a refrigeration plant of the kind used for controlling the flow of refrigerant from the evaporator to the compressor. The closure member for the valve unit is controlled directly or indirectly by a reference pressure generator having an expansible chamber filled with a refrigerant medium having vapor and liquid phases. The pressure exerted by the vapor phase of the medium provides a bias for controlling the valve and is directly related to the temperature of the liquid phase. A heat transfer element such as a heating resistor in the liquid phase is heated or allowed to cool in a controlled manner by an external control unit. A temperature responsive sensor element in the liquid phase of the medium is part of a feedback system for the control unit which allows a selected temperature to be maintained in the chamber which results in a desired constant pressure in a valve opening direction to be maintained in a chamber. A control circuit has an evaporator parameter input branch and a second input branch for the feedback temperature sensing element. The control unit has an output for heating the heating resistor in the expansible chamber and a summating section for varying the relative effects of the input branches on the output.

Compact heat pump device

Abstract: The invention relates to a compact heating assembly of the heat pump type, comprising a heat pump circuit having a compressor, an evaporator and a condenser, wherein the evaporator and condenser parts, together with means for heat exchanging heat carrying fluids against the same, are arranged in a housing. The evaporator and its heat exchanger means and the condenser and its heat exchanger means substantially form an essentially vertical helical conduit system which encloses an inner space, wherein the compressor, possible circulation pumps, etc. are arranged. The device can be burrowed in the ground, and the inner space is accessible via an inspection cover arranged at the top.

Lubricant Related Problems with Heat-Pumps

Abstract: Roger Morgan, Lecturer, Brian L. Sutcliffe, Laboratory Technician, Oil is required in refrigeration and heat pump systems for lubrication of the compressor, expansion valve and other moving p~rt7. Ho~ever, the oil is often highly m~sClble wlth the refrigerant, in proportlons which depend on pressure and temperature, as well as oil and refrigerant type. As some of the oil circulates around the system with the refrigerant, it follows that at all times a proportion of the refrigerant will be dissolved, as a liquid, in the oil. Not only does this oil-refrigerant miscibility give rise to dilution of the oil, hence impairing its lubricating properties, but it also leads to a reduction in evaporator capacity. This is because, at the evaporator outlet, some of the refrigerant remains in the liquid state, dissolved in the oil, and is thus unavailable for evaporation to carry latent heat. This effect on its own would not be too serious, were it not that the coefficient of performance (COP) is also impaired due to oil circulation. This results from the fact that, while evaporator capacity is reduced, compressor power is largely unaffected by the oil circulation rate. This of course implies a reduced COP. In a heat pump design, COP is usually all-important, and this paper examines some of the effects of oil circulation on heat pump performance. Particular attention is drawn to designs using oil-flooded rotary sliding-vane compressors, where oil circulation is usually much 156 School of Physical Sciences, The New University of Ulster, Coleraine, Northern Ireland. School of Physical Sciences, The New University of Ulster, Coleraine, Northern Ireland. School of Physical Sciences, The Ne~ University of Ulster, Coleralne, Northern Ireland. School of Physical Sciences, The New University of Ulster, Coleraine, Northern Ireland. School of Physical Sciences, The New University of Ulster, Coleraine, Northern Ireland. greater than with reciprocating compressors. BACKGROUND In this laboratory we have been concerned fo:t:· some time in the design and development of vapour compression heat pumps for a range of applications, and it has usually been our experience that performance is not quite as good as would be expected from the compressor manufacturer's performance charts. There are many reasons for this, but the short-fall in performance is not usually very great. However, recent tests using a rotary sliding-vane compressor showed up an abnormally wide and unacceptable discrepancy between observed performance and the manufacturer's data under certain conditions. Another factor was the consistent measurement of liquid line temperatures several degrees above saturation. These readings, indicating superheat, were somewhat puzzling as we could clearly see liquid refrigerant in the sight glass. After these obs~rvations, the accuracy of our measuring i~struments was thoroughly checked, and the tests repeated, still with the same results. At this point we realised that the effects of oil-refrigerant miscibility could be more important than we had thought previously, and a fairly trivial calculation using Raoult's Law showed that the presence of oil in small amounts could change the saturation temperature to the observed extent. From here our investigations followed in the footsteps of such as Bambach (1955) and Spauschus (1963). OIL-REFRIGERANT INTERACTION Oil is miscible with fluorocarbon refrigerants to a varying degree. In the case o~ liquid Rl~ it is totally miscible, the m~xture form~ng a single phase at all temperatures and pressures. The effects produced by the oil in a heat pump system can be summarised as follows: 1. It changes the working fluid from a pure refrigerant with well known properties to a poorly understood mixture, with properties which depend on the oil type and concentration. 2. It can affect the heat transfer processes in the evaporator and condenser. This effect can be either to improve or impair heat transfer, depending on oil concentration (Green, 1963) . 3. The boiling point of the mixture is elevated above that of the pure refrigerant, according to Raoult's Law. 4. The heat carrying capacity of the mixture is reduced during evaporation because the oil holds a proportion of the refrigerant in the liquid phase, thereby reducing the latent heat pick-up. As will be shown later, this effect implies a reduction in the coefficient of performance (COP). It follows from these points that the presence of oil in a heat pump circuit could have a significant effect on its performance. The following analysis is an attempt to predict and quantify the likely effects.

Airrconditioner with refrigerator

Abstract: PURPOSE:To devise to drive a refrigerator independently as well as to keep its refrigerating effect free from the influence of the driving state of a car in a titled unit for automobile by switching over electromagnetic valves provided on a refrigerator entrance pipe and a bypass valve properly and selectively. CONSTITUTION:A refrigerator entrance pipe 7 is connected with the preceding stage of an expannsion valve 3 on the side of an air-conditioner, and on the way of this entrance pipe 7, a bypass pipe 13 is provided to return refrigerant to a compressor 1. On the preceding stage of an expansion valve 3 of an air-conditioning circuit, the bypass pipe 13, and the rfrigerator entrance pipe 7, electromagnetic valves 15, 16, and 17 are respectively provided to be selectively switched over. For operating an air-conditioner and a refrigerator simultaneously, swithes 19 and 21 are put to ON to release electromagnetic valves 15 and 17, and refrigerant is given to sides of the expansion valve 3 and a throttle 8. Meanwhile, for refrigerating the contents of the refrigerator quickly, only the electromagnetic valve 17 is put to OFF, and electomagnetic valves 16 and 17 are put to ON for operating the bypass pipe 13.

Refrigeration compressor capacity control means and method

Abstract: A capacity control for a multi-cylinder refrigeration compressor includes a modulating valve disposed between a suction manifold and less than all of the cylinders of the refrigeration compressor. The modulating valve regulates the flow of refrigerant gas from the manifold to the cylinders in communication therewith, with the valve functioning to increase the flow of refrigerant gas to the cylinders as the load on the refrigeration unit increases and to decrease the flow of refrigerant as the load on the refrigeration unit decreases.

Heat pump for heating system - uses heating medium to cool engine driving compressor

Abstract: The heat pump for heating purposes comprises a heat absorber, an evaporator and a condenser with heat exchanger. A refrigerating medium circuit through evaporator and condenser has a compressor before the condenser and an expansion valve before the evaporator. A heat-transfer medium circuit through absorber and evaporator includes a heat pump, and the compressor is driven by an engine with a cooling system. The cooling system (11) of the engine (10) is cooled by the medium of the heating circuit (9) between the absorber (1) and evaporator (2).

Stored fuel element heat recovery - by ammonia circulating through evaporator, turbine- and condenser

Abstract: Surplus heat form nuclear fuel elements which are stored in an intermediate storage basin is recovered by circulating a heat carrier agent such as NH3, which boils at low temp., by a pump through an evaporator, suspended inside the basin. The vapours, produced by it, are passed to a prime mover such as a turbine for conversion into mechanical work. The agent is liquefied in a condenser and is returned by the pump to the evaporator. Such a system is independent of any extraneous energy input. It operates profitability and helps to reduce the intermediate storage costs.

Compressor refrigeration circuits

Abstract: A closed refrigeration circuit comprises in series a compressor, a condenser, a drier-filter, a capillary tube, an evaporator, and a conduit connecting the evaporator to the condenser and traversing the drier-filter. A refrigerant fluid circulates in operation through the circuit. With this arrangement the connecting conduit is in heat-exchanging relationship with the drier-filter, thereby avoiding the need for a separate heat exchanger.

Method for defrosting a refrigeration system

Abstract: Apparatus and a method for operating a refrigeration system without reverse cycle defrost are disclosed A heat exchanger is divided into a plurality of zones, one zone being constantly utilized as a subcooler to both defrost said zone and to subcool the refrigerant The remaining zones of the heat exchanger are utilized as an evaporator as is known in the art A selector valve which is capable of indexing liquid refrigerant flow between zones and receiving gaseous refrigerant from the remaining zones is also disclosed Additionally, a header arrangement having both expansion means and a conduit controlled by check valve is utilized to direct refrigerant flow from the subcooled zones to the remaining zones of the heat exchanger which act as an evaporator

Refrigerator with a large refrigeration chamber cooled by natural convection

Abstract: Refrigerator having a large volume refrigeration chamber cooled by natural convection, including a defrostable finned evaporator disposed in upright position in the chamber, the evaporator being subdivided into at least two sections connected together in series in a refrigerant flow path, a view shield serving as an air baffle disposed in front of the evaporator, and a substantially horizontally disposed partition occupying substantially the entire usable cross sectional area of the chamber, the partition having an edge extended between the sections of the evaporator.

Control apparatus for the low pressure evaporator of a refrigeration plant

Abstract: The invention relates to control apparatus for feeding liquified refrigerant to the evaporator of a refrigeration system. A main valve controlled by a differential pressure type servo-element controls the flow of refrigerant to the evaporator. A float type pilot valve has a nozzle and closure member controlled by a float which has a liquid level identical to liquid level in the evaporator. A pilot conduit which extends between the main valve and the pilot valve has first and second throttle units arranged in series. The first throttle unit controls a flow of liquid refrigerant through the pilot conduit to control the main valve. The second throttle unit controls a flow of refrigerant through the pilot conduit which is at least partially in vapor form. This arrangement with two throttle units allows control over a broader proportional range for the settings of the float in the pilot valve.

Combined heat pump and solar heater - are alternatively connected to heat store by automatic control unit dependent on temp.

Abstract: The method of heating a house combines a solar heating system (1) with a heat pump using a set of heat exchanger coils (2,3,5) buried underground. These are interconnected with a latent heat store (10) enclosed in insulation (11), which stores heat sufficient for the requirements for a whole day. The store houses the condenser (7) for the heat pump, this being connected by a compressor (6) and expansion valve (8) to the evaporator (9). The line to the solar heater includes a pump (15) and check valve (17) also the line between the buried coil (5) and the heat store includes a second pump (16) and check valve (18). These are connected to valves (19,20) operated by thermostats in an automatic control system so that the heat store is connected either to the solar heater or to the heat pump, whichever is hotter. The solar heater can also be connected to the heat pump.