US20030097856A1

US20030097856A1 - Regulator with receiver for refrigerators and heatpumps

Info

Publication number: US20030097856A1
Application number: US10/204,663
Authority: US
Inventors: Warwick Stokes
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-03-13
Filing date: 2001-03-05
Publication date: 2003-05-29
Also published as: DK174179B1; ATE303566T1; NO20024334D0; NO325992B1; DE60113072T2; NO20024334L; WO2001073360A1; EP1264150B1; DE60113072D1; AU2001240471A1; EP1264150A1; DK200000398A

Abstract

The regulator is a refrigerant regulator intended for heatpumps and refrigerators. It has a built-in receiver, which automatically absorbs redundant refrigerant. It is a hermetic closed device without removable parts. It is robust and there is no need for adjustment. The regulator is composed of a heat exchanger with large heat capacity, a receiver and two pressure reducing valves. The two valves behave different on boiling fluid flow. One of them, named a heat sensitive valve, restricts fluid flow when the fluid is boiling. In the other valve, named a pressure sensitive valve, the boiling has no influence on the fluid flow. The regulator controls the refrigerant flow from the receiver to the evaporator by means of the pressure in the receiver—and the pressure in the receiver is controlled, via the heat exchanger, by the need of refrigerant in the evaporator. This way of control ensures 100% use of the evaporator, the suction gas is superheated, and the liquid from the condenser is sub-cooled. These factors improve the relation between the cooling capacity and the power consumption with more than 10%.

Description

This invention relates to refrigeration circuits as described in the first part of claim 1. A circuit like this is known from U.S. Pat. No. 2,520,045, wherein the flow of refrigerant, between receiver and evaporator, is regulated by the difference between the pressure the evaporator and the pressure in the receiver, which correspond to the temperature at the exit of the evaporator. I this way the difference in pressure between the evaporator and the receiver correspond to the superheat of the evaporator. This interaction makes a self-balancing effect, because increasing superheat causes increasing flow, which causes decreasing superheat—and contrary. That means that the flow of refrigerant to the evaporator is controlled by the superheat of the evaporator, just like an ordinary, thermal expansion valve.

The invention distinct from the above mentioned by the evaporator is completely inundated and the suction gas is supersaturated, which means that the suction gas leaving the evaporator contains refrigerant in liquid state. The temperature in the receiver is controlled by heat exchange between the liquid from the condenser and the supersaturated suction gas. This causes a self-balancing effect because when the fluid content of the suction gas decreases then the temperature of the receiver increases, whereby the flow to the evaporator increases, and the fluid content of the suction gas increases—and contrary. In this way, the flow of refrigerant to the evaporator is controlled by the fluid content of the suction gas.

To obtain the mentioned self-balancing effect, it is an indispensable assumption that the flow of refrigerant from the receiver to the evaporator increases/decreases when the temperature in the receiver increases/decreases. Using an ordinary capillary tube between the receiver and the evaporator, like U.S. Pat. No. 2,520,045, this assumption is only fulfilled when the temperature difference, between evaporator and receiver, is less than three Kelvin. If the difference exceed three Kelvin, the refrigerant is boiling so much, in the capillary tube, that the flow decreases when the temperature difference increases. Boiling refrigerant in the capillary tube can be avoided by establishing heat exchange between the refrigerant entering and leaving the capillary tube.

With a SelfCoolingValve, described in the first part of claim 2, boiling in the capillary tube can be avoided by subcooling the refrigerant before entering the capillary tube. The subcooling is realized by placing the valve at the entry of the evaporator or in a tube placed in continuation of the entry.

The technique of cooling refrigerant at the entry of the evaporator is known from U.S. Pat. No. 2,956,421, where same part of a capillary tube extends into the evaporator, makes an U-turn, and ends up at the entry point, where the discharging refrigerant flows across the capillary tube and cools it. The SelfCoolingValve distinct from U.S. Pat. No. 2,956,421by a heat exchanger, placed before the capillary tube, wherein the refrigerant is subcooled to the same temperature as the evaporator, before entering the capillary tube, and thereby boiling in the capillary tube is avoid.

If the time for changing the fluid content of the suction gas is longer, than the time for changing the corresponding pressure in the receiver, it causes resonance between the evaporator and the receiver. This problem can be avoid by assigning an adequate heat capacity to the heat exchanger, which can be achieved by placing the heat exchanger in contact with a water reservoir, like an outer shell filled with water.

The present invention provides a refrigeration system where the evaporator is inundated, the suction gas is superheated before it come to compressor and the liquid from the condenser is sub-cooled. All three factors contribute to increase the Coefficient Of Performance (COP). Calculations confirmed by test show that the COP is increased by more than ten percent.

EXPLANATION OF THE DRAWINGS

FIG. 1 is a diagranumatic view of the SelfCoolingValve. It is composed by an inner tube ([0008] 1) connected by a capillary tube (2) to en outer shell (3). The flow is from (4) to (5). The outer shell (3) is either the entry of the evaporator or it can be a tube placed in continuation of the entry (5).
FIG. 2 is a side view of the heat exchanger. It is build from three concentric tubes ([0009] 6), (7) and (8).
The inner tube ([0010] 8) is for the suction gas, which flows from (9) to (10).
The middle tube ([0011] 7) makes a shell around the inner tube. It has a connecting-piece at top (11) and bottom (12). Fluid flows from (11) to (12).
The outer tube ([0012] 6) makes a shell around the middle tube. It contains frost-proof water, and is made hatch on the drawing.
FIG. 3 is a top view of the heat exchanger. The numbers have the same meaning as in FIG. 2. [0013]
FIG. 4 shows a diagrammatic view of a refrigerating system embodying a compressor ([0014] 16), a condenser (15), an evaporator (13) and a regulator (14).
The regulator is composed by a HeatSensitivValve ([0015] 17), a heat exchanger (18), a receiver (19) and a PressureSensitivValve (20). The heat exchanger (18) is shown in more details in FIGS. 2 and 3.
Construction [0016]
The regulator is composed of four parts: [0017]
[0018] 17. HeatSensitivValve
[0019] 18. Heat exchanger with large heat capacity
[0020] 19. Receiver
[0021] 20. PressureSensitivValve
The numbers refer to FIG. 4. [0022]
HeatSensitivValve [0023]
This valve must comply with two demands: [0024]
Increasing pressure across the valve—increasing flow of refrigerant [0025]
Increasing temperature drop across the valve—decreasing flow of refrigerant [0026]
A capillary tube complies with these demands. The diameter and length of the capillary tube can be calculated or found by experiment. [0027]
Heat Exchanger with Large Heat Capacity [0028]
The purpose of the heat exchanger is to transfer heat from the liquid from the condenser to the suction gas. The heat exchanger must have a large heat capacity, to suppress resonance between the evaporator and the receiver. The heat capacity of the heat exchanger must be so large, that the pressure in the receiver reacts slower, than the fluid content of the suction gas, in respond to a change in the flow of refrigerant. [0029]
An appropriated heat capacity can be obtain by incorporating a reservoir with frost-proof water. [0030]
FIGS. 2 & 3 show an instance composed by three concentric copper tubes. [0031]
The outer tube ([0032] 6) makes a container with a suitable quantity of frost-proof water.
In the middle tube ([0033] 7) the liquid flows from top (11) to bottom (12)
In the inner tube ([0034] 8) the suction gas flows from top (9) to bottom (10)
Receiver [0035]
The receiver ([0036] 19) must be large enough to contain all of refrigerant in the system.
PressureSensitivValve [0037]
This valve must comply with two demands: [0038]
Increasing pressure across the valve—increasing flow of refrigerant [0039]
The flow through the valve must not react on temperature change. [0040]
That can be a capillary tube if the flow is subcooled down to the end temperature, before entering the capillary tube. [0041]
The SelfCoolingValve shown in FIG. 1 has this property. Warm refrigerant enters at ([0042] 4). In the tube (1), the flow is cooled to the same temperature as outside the tube. The refrigerant flows through the capillary tube (2) without boiling. From the capillary tube, the refrigerant discharges at the bottom of the outer tube (3). The refrigerant flows over the outside of the inner tube and hereby the tube is cooled. The refrigerant is boiling while absorbing heat. Fluid and vapour are flowing into the evaporator at (5).
Principle of regulation. The numbers are referring to FIG. 4. [0043]
When the refrigeration system starts, the compressor ([0044] 16) suck in vapour from the evaporator (13). Hereby the pressure in the evaporator drops and the evaporator suck in fluid via the valve (20) from the receiver (19).
In the condenser ([0045] 15) the pressure rises and warm fluid flows through the HeatSensitivValve (17). Caused by the drop i pressure in the valve (17), the refrigerant is boiling and a mixture of fluid and vapour flow into the heat exchanger (18). In the heat exchanger, vapour condenses doing heat ejection into the suction gas and the mass of the heat exchanger, causing the temperature to rise—slowly because of the large heat capacity.
As the temperature rises in the heat exchanger, the pressure in the receiver rises too and the flow of refrigerant into the evaporator increases. [0046]
After some while the evaporator is inundated and the suction gas contains refrigerant in liquid state. The liquid strongly affect the heat exchanger, where the temperature starts to go down—slowly because of the large heat capacity. [0047]
As the temperature in the heat exchanger falls, the pressure in the receiver falls too, and the flow of refrigerant into the evaporator decreases. [0048]
When the flow of refrigerant into the evaporator decreases, the fluid content of the suction gas decreases and thereby the cooling effect in the heat exchanger decreases, causing the temperature to rises. [0049]
The temperature in the receiver stabilizes, when the heat exchanger attains equilibrium between heat from condenser and cooling effect from the suction gas. [0050]

Claims

1. A refrigeration circuit comprising compressor (16), condenser (15), evaporator (13) and with heat transfer between suction gas and liquid from the condenser in heat exchanger (18) and where there between condenser and heat exchanger is capillary throttling (17) of the refrigerant and receiver (19), capillary throttling (20) from receiver to evaporator characterised in that capillary throttling (20) occurs during heat transfer between the refrigerant entering the capillary tube and the refrigerant leaving the capillary tube and the heat exchanger (18) is worked out with large heat capacity.

2. A closed refrigeration circuit as claimed in claim 1 with the capillary throttle (20) between receiver (19) and evaporator (13) elaborated like a SelfCoolingValve as showed on FIG. 1, composed of an outer shell (3), a heat exchanger (1), entering into a capillary tube (2), which free end is leaded up to the entry point of the heat exchanger, characterised in the fluid at entry of the valve (4) is subcooled down to the temperature at the exit of the valve (5), before the fluid reachs the capillary tube (2).

3. A closed refrigeration circuit as claimed in claim 1, characterised in that the heat exchanger (18) has thermal contact with a reservoir of water, which contribute to the heat capacity of the heat exchanger.