JPH02263071A - Using method for expansion valve device and assembly of vaporizer and flow rate control means - Google Patents

Abstract

PURPOSE: To enable the reliable measurement with a bulb which receives a hot or cold gas from a flow of a gas directly delivered from an evaporator, by a method that a pressure difference measuring unit acts against pressuring means to control the position of a flow rate control means and bulb approaches to a discharge pipe of the evaporator and supports a heating means and part of the bulb is located in the discharge pipe. CONSTITUTION: When a compressor 101 operates with full load, a resistor 20 is energized to heat a liq. 8 in a bulb 104 to push a spring 17 enough to open a piston 15, thereby flowing a liq. refrigerant from a condenser 102 into an evaporator 2. If the heat quantity obtd. from a circulating water in a vessel 4 lacks, the refrigerant fluid cannot enough evaporated by the evaporator 2, liq. droplets appear in a discharge pipe 1. When the carried liq. droplets begin to collide against a region 27 of the bulb 104, the bulb is cooled to reduce the pressure therein to reduce the pressure on a film 10, thereby closing the piston 15. A region where heat is given to the bulb and region where cold gas is received by the bulb and liq. housed therein are closely adjacent and hence the heat quantity need not move over a long Cu strip and hence an expansion valve 103 opens sensibly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method of using a thermal expansion valve device comprising a valve (spherical body) at least partially filled with liquid.

The invention also relates to an evaporator and flow control means assembly.

The invention further relates to a refrigeration machine.

[Conventional technology]

As is well known, refrigeration machines, such as those used for example for refrigeration or for air conditioning, are equipped with a compressor for compressing a refrigerant fluid in the gaseous state. This fluid is cooled and condensed by contacting a so-called "heat source" (not hotter than the gas coming from the compressor), and the pressure of this condensed fluid is then increased by contacting a so-called "cold source". The pressure is reduced through an expansion valve to a pressure low enough to evaporate the fluid, after which the evaporated gas returns to the compressor.During this evaporation, the fluid absorbs heat from the cold source; This produces the desired refrigeration effect.

This type of machine needs to be controlled to avoid two drawbacks. If the amount of heat available at this cold source was low, a large amount of unevaporated liquid would be returned to the compressor. This damages the compressor and in any case results in wasted energy of the machine (the machine produces more cold air than necessary). On the other hand, if the amount of heat available at the cold source was high, the liquid flow rate reaching the evaporator would not be high enough to maintain the cold source temperature at the desired low level.

To accomplish such refrigeration, the expansion is accomplished by using a thermal expansion valve, i.e., an expansion valve connected to a valve partially filled with the same fluid normally used in the refrigeration circuit. It is known to control valves and evaporators. The membrane is exposed on one side to the pressure in the valve and on the other side to the pressure in the evaporator. The membrane acts against the biasing spring on the valve flow control means of the expansion valve. A valve is normally mounted at the outlet of the discharge pipe through which the refrigerant fluid exits the evaporator and is directed to the compressor, and flow control means are provided to ensure that superheating of the gas causes the liquid in the valve to -
Opens only when heating to the point where this pressure exceeds the pressure in the evaporator by the amount of pressure given by the spring.

The disadvantage of this type of control is that it requires superheating to operate. In fact, according to the laws of thermodynamics, in the absence of superheating, i.e. when there is a mixture of liquid and gas in the discharge pipe, the temperature in the discharge pipe is largely a function of the pressure; is not a function of percentage. Since the pressure inside the valve is a function of temperature only,
The pressure in the valve is the same regardless of the proportion of liquid in the evaporator discharge pipe, and no adjustment is possible.

Such superheating as is necessary for conditioning means that the evaporator has to be substantially larger, which significantly increases costs; It is much lower than the current area.

In an air conditioner intermediate medium called water chillers, i.e. water is cooled and then the air is cooled.
The size of the evaporator can be roughly divided in half when the normal 5°C superheat is no longer present.

This means that the average temperature difference between the water and the refrigerant itself is 5°C.
This is not surprising given that heat exchange with the original gas is extremely inefficient at such a low temperature difference of only ~7°C.

Since the cost of such an evaporator is 20 to 30% of the total air conditioner, the actual cost savings are significant.

Attempts have been made to reduce superheating with electronic expansion valves that essentially measure the temperature of the gas and evaporator liquid to control the valve electronically. However, such electronic expansion valves are very expensive, and nevertheless these valves typically require 2-3°C superheating to operate, so no real savings are possible. Ta.

Attempts have also been made to displace the operating point of a thermal expansion valve by using a valve and heating the valve with other heating means such as an electrical resistor; this method is described, for example, in U.S. Pat.
7. Seen in No. 613. However, such a method requires difficult matching of the ohmic values of the resistors, and this matching is not suitable for various operating conditions.

[Problem to be solved by the invention and means and action for solving the problem]

A first object of the present invention is a method of using a thermal expansion valve device, the valve device comprising a valve at least partially filled with a liquid and connected to one side of a differential pressure measuring device; The other side of the measuring device is exposed to the pressure within the evaporator, said differential pressure measuring device acting against the biasing means to control the position of the flow control means, said valve being adapted to control the discharge of said evaporator. It is characterized in that it is connected to a pipe and carries heating means, the valve being at least partially located within the discharge pipe.

A second object of the invention is an assembly of an evaporator and a flow control means, the assembly comprising: a refrigerant inlet connected to a thermal expansion valve; and a valve at least partially filled with liquid. - a differential pressure measuring means having a first input connected to the valve and a second input exposed to the pressure within the evaporator; means for positioning the flow control element of the thermal expansion valve as a function of the differential pressure measured by the differential pressure measuring means; and heating means coupled to the valve, the valve at least partially evaporating. It is characterized in that it is installed in the discharge pipe of the vessel so that at least a portion thereof is exposed to the flow of refrigerant in the discharge pipe.

A third object of the present invention is a refrigeration machine, which is equipped with an assembly of an evaporator and a flow control means according to the second object.

When the gas leaving the evaporator becomes wet, i.e. contains droplets, these droplets impinge on the valve and very quickly cool the liquid in the valve, thereby reducing the pressure in the valve. Therefore, the flow rate control means is closed. On the contrary,
As the gas leaving the evaporator dries, the cooling action of the refrigerant gas on the liquid in the bulb becomes less effective, and the electrical resistor brings the liquid in the bulb to a higher temperature than the temperature of the refrigerant gas surrounding the valve. It begins to heat up, thereby causing the valve to believe that the gas is superheated and causing the flow control means to open.

In fact, and in contrast to the prior art, according to the invention the gas emitted by the evaporator often contains some liquid instead of being sufficiently vaporized and superheated.

Although this has little or no effect on the efficiency of the device, it is important to note that in most cases the gas coming from the evaporator is used to cool the electric motor that drives the compressor. It is immaterial whether this loss is obtained by heating the dry gas and expanding its volume or by evaporating the liquid of the wet gas.
The reason is that in both cases the volume to be compressed and the energy required to compress this volume of gas will be the same.

In addition to allowing very practical cost improvements,
The O'C superheat expansion valve of the present invention provides several significant benefits.

Firstly, the reaction time is so fast that the invention is virtually free from erratic operation. This results from the fact that the valve pressure equilibrium is dictated by the liquid phase on both sides of the valve wall instead of the gas on at least one side (usually the outside) of the valve wall, and this affects the transfer efficiency. It will increase it by 10 times.

This is not the case for structures where the valve is completely external to the discharge pipe, as shown in US Pat. No. 446'7613, and in such cases the heat transfer that can be eliminated by the present invention There is a delay.

Moreover, the present invention can eliminate one of the main drawbacks of the prior art according to US Pat. No. 4,467,613, namely operational uncertainty. In fact, even when the gas emitted by the evaporator contains no liquid, the outer bulb heated by the resistor acts as if it contained more liquid due to the large amount of heat absorbed by the pipe. This can occur when there is a liquid on the inner wall of the pipe, which may be, for example, oil returning to the compressor or residual droplets of liquid refrigerant that have not yet fully evaporated. I can do it.

According to the present invention, these major drawbacks are eliminated and reliable measurements are made possible because the valve receives and extracts its heat or cold directly from the gas flow exiting the evaporator.

According to a preferred feature of the invention, the valve is thermally isolated from the discharge pipe and is not thermally influenced by the liquid along the wall of the discharge pipe.

Such insulation is for example a plastic element, which has the advantage of being easily deformed and at the same time providing a good leaktight seal between the valve and the discharge pipe, even though the valve is usually not perfectly cylindrical. It can be done.

There is also a second category of advantages of the present invention. Basically (as is known) thermal expansion valves are not suitable for precisely controlling evaporators over a very wide range of capacities. When suitable for proper operation, the refrigerant flow should be one-third of the full load.
It will not work if it is lower. This means that two
One or three valves should be used in parallel to ensure that the refrigerant flow to the evaporator is still controlled when the device and therefore the compressor must operate in the 10-30% capacity range. It means that.

The present invention has the unexpected effect of overcoming this drawback. More specifically, the present invention uses the same valve to operate the refrigeration system over the entire range of operation and typically at 10-20% of full load.
to be able to control it.

More specifically, in a preferred embodiment of the invention,
The heating means is partially or completely shut off when the required cooling capacity falls below a certain value, for example 50%. This shutoff is performed by controlling the capacity of the compressor. (The compressor is provided with a capacity control means which normally operates automatically to match the amount of compressed fluid produced by the compressor to the flow rate of refrigerant fluid through the evaporator.)
When the heating means are switched off (or alternatively partially disconnected), the valve operates as a standard valve, ie seeks superheat from the evaporator. This is possible at partial load even though the evaporator is of relatively small size in terms of its possible cooling capacity at full load.

Also, according to the invention, nothing prevents the construction of the valve from setting the spring to double or triple the superheat required for maximum opening of the valve; This is because superheat is provided by the heater. This still provides a large amount of superheat and spring bias available at part load, and makes the valve responsive to much lower flow rates than in the prior art, as explained below.

〔Example〕

The invention will be better understood from the following description of embodiments of the invention by way of non-limiting example and with reference to the accompanying drawings, in which: FIG.

As shown in FIG. 2, one example of a refrigeration machine includes a compressor that compresses a gaseous refrigerant fluid and discharges the fluid into a condenser 102 where the fluid is condensed. This condensed fluid passes through a duct 18 to a controlled expansion valve 10
3 to reduce the refrigerant fluid pressure and then to duct 1
9 through which the fluid is evaporated and absorbs heat. The refrigerant discharge pipe 1 of the evaporator 2 is connected to the inlet of the compressor 101. The evaporator 2 comprises a refrigerant pipe 3 in a container 4 in which the water to be cooled circulates along arrows 6 and 7 between a water intake pipe 5a and a water outlet pipe 5b.

The expansion valve comprises a membrane 10, one side 11 of which is fixed to the refrigerant discharge pipe 1 of the evaporator and is connected to a valve (described below).
sphere) 104 and the other side 12 of the membrane 10 is connected to the discharge pipe 1 by an external pressure equalization line 13.
Exposed to internal pressure, this membrane 10 forces the flow control piston 15 away from its seat 16 against the biasing force of the spring 17 via the rod 14.

The pressure within the valve 104 is transmitted to the side surface 11 of the membrane 10 by a pressure transmitting means such as a capillary tube 9.

The bottom portion of the bulb is surrounded by an electrical heating resistor 20 made in a known manner on a plastic foil partially coated with a resistive material seen at 26 and wrapped around the bulb; This is held and pressed against the valve by a cover 41, usually made of plastic. Current is passed through resistor 2o by wires 21 and 22
is supplied to

The valve is held in the pipe 1 by a metal flange 23, which has a conical hole 23a passing through it.
into this hole 23a a plastic cone 24, for example made of PTFE (polytetrafluoroethylene), is pressed by a flange 25. The plastic cone 24 has a cylindrical through hole extending axially through it, and the valve 104 and the wires 21 and 22 are mounted in the cylindrical through hole in a leak-tight manner. The plastic cone deforms to provide a passage for the wires 21 and 22 and sealingly isolates the interior of the pipe l containing the refrigerant gas and liquid from the outside air. The plastic cone 24 holds the valve 104 across the pipe 1 in a position where the main part of the valve 104, in particular the bottom part, extends into the interior of the discharge pipe 1.
It is exposed to the flow of refrigerant inside.

The plastic cone 24 further provides the valve with insulation against heat or cold entering from the wall of the pipe 1. This causes the temperature inside the valve to vary between the amount of heat generated by the resistor and the area of the pipe exposed to the flow of refrigerant.
basically depends on the amount of cooling received.

This device operates as follows.

When the compressor 101 is operated at full load, the resistor 20 is energized and heats the liquid 8 in the valve, thereby causing the valve and membrane lO
increases the pressure inside the volume adjacent to the side 11 of the evaporator 2 and then presses the spring 17 to open the piston 15 and allow the liquid refrigerant coming from the condenser 102 to flow into the evaporator 2.

If the amount of heat available from the water circulating in the container 4 becomes insufficient, this refrigerant fluid can no longer be sufficiently evaporated in the evaporator 2 and droplets of liquid appear in the discharge pipe 1. . Only at this stage, i.e. when drops of liquid carried along the interior of the pipe l begin to impinge on the area 27 of the valve, does the valve cool and the pressure within the valve decreases, thereby reducing the pressure on the membrane 10. so that the piston 15 gradually closes. An important feature of the invention is the close proximity between the area where heat is applied to the valve and the area where cold air is received by the valve and the liquid contained therein, so that the amount of heat is It should be noted that it is ensured that there is no need to travel through a long piece of copper. , such movement limits the rate of heat transfer and (a) creates a final equilibrium pressure within the valve so that the expansion valve is dependent on a second factor, such as ambient temperature, which has no effect on the control device. (b) The response of the valve 103 to changes in the situation is delayed and reliability is obtained against irregular operation of the valve.

FIG. 3 shows the results produced by the invention, showing on the positive abscissa the percentage by weight of liquid carried by the moist gas, with the vertical line 28 corresponding to 0% of the liquid but the gas being superheated. The negative side of the abscissa indicates the amount of superheat and the ordinate indicates the pressure differential across the membrane.

As an example of numerical values, the diameter is approximately 15mm and the length is 110mm.
The no valve actuates an expansion valve installed in a pipe approximately 7011II11 in diameter and operates a 50 ton air conditioner, which is operated with refrigerant R-22 and the evaporation temperature is set at 7°C. The amount of liquid in this valve is limited so that it is completely evaporated when the differential pressure reaches approximately 3 bar, as shown in Figure 29, at which point the valve is sufficiently opened to prevent further pressure. The superheat prevents the valve from opening further; the superheat at this point is about 1°C.

reach.

As the flow control means 15 opens further, the pressure continues to fall until it reaches a value 30 approximately equal to 1 bar, and the amount of liquid carried by the gas in weight percent reaches a value 30, which in this case is approximately 1 percent. . A further increase in the liquid content artificially injected into the upstream pipe of the valve does not reduce the pressure difference, so the tension of the spring is such that the pressure difference across the membrane 10 is 1 bar when the piston 15 is fully closed. It is set so that

The result is that maximum capacity is achieved with a superheat of 1 degree instead of the usual 5 or 6 degrees, thereby eliminating a large portion of the evaporator's superheat generation area.

Of course, by increasing the capacity of the resistor, we can displace the curve of Figure 3 towards the right, so that instead of operating the valve partially in the superheat region, it operates almost completely in the wet region. This can help increase the cooling capacity of the evaporator and increase the amount of liquid that is passing through the device without being evaporated.

According to an advantageous feature, at partial load the power generated by the resistor 20 can be reduced or even zero;
This thermal expansion valve can then be operated in a normal manner.

FIG. 4 illustrates the advantages obtained.

This shows the opening amount of the valve 103 on the ordinate and the pressure difference on the abscissa, where curve 32 is the curve of a conventional valve;
Curve 33 is the curve of the preferred embodiment of the invention.

As is known, a standard thermal expansion valve begins to open when the pressure differential imposed by superheating reaches the value shown at 34 and is sufficiently relieved to the differential pressure 35.

Since the total superheat must be limited in order not to increase the size of the evaporator too much, the slope of curve 32 must be steep, so that the sensitivity of the opening to changes in superheat is very high. , the action of the valve is therefore less precise, and furthermore, when the amount of superheating decreases to the point where the pressure difference approaches a value of 34, the opening of the valve becomes variable; one reason is that in most valves the piston 15 34 because there is no pressure equilibrium on its two sides, which closes and remains closed or opens and remains open, which corresponds to a partial load condition of approximately 35% or less than 40%. will not be well controlled in the pressure differential area near .

According to the invention, the maximum superheat exhibited by the valve is
Since it is done by a resistor and not by superheating of the evaporator gas, it is no longer limited, and also allows for greater sensitivity and still maintaining a large differential pressure across the membrane even at part load. , and can be operated under non-steep slopes.

This valve can therefore be operated at 20% load or even lower if necessary, thereby eliminating the need for multiple valves operating in parallel.

Additionally, the opening point is shifted to the right, to a position such as 36, where the valve can operate even hotter than normal, so that when the device is in no-load operation on a hot day, the valve will open the expansion valve. Reduces the risk of flooding the evaporator.

According to the invention, the resistor can be mounted inside the valve instead of around it, the valve can be mounted diagonally or horizontally instead of vertically, and the outer pressure equalization line can be mounted inside the valve instead of around it. The internal pressure equalization device can be replaced or connected to other parts of the low-pressure part of the refrigeration machine, i.e. between the expansion valve outlet and the compressor inlet, and the valve can be replaced by a straight tube with a different shape, e.g. The resistor shown at the bottom of the valve, which can be curved, can be installed in the cooling area in contact with the moist gas in the upper, lower part, in the same valve as in refrigeration equipment. Instead of using one fluid, a different fluid can be used, the amount of fluid in the valve is limited to limit the maximum pressure above the rise to the value obtained when sufficient fluid has been evaporated, and the electric heater is Alternatively to using heat can be generated by other means such as a burner and this heat can be conveyed to the valve by heat transfer means such as heating tubes;
The membrane can be biased using springs and different means, such as gas pressure, and this membrane can be replaced by other differential pressure measuring devices, such as pistons, and at part load the heater It should be noted that the no load can be gradually disconnected in stages from 100% heating to 0% for the refrigeration load. Furthermore, the valve 104 does not necessarily have to be fixed to the discharge pipe 1 via insulation means (cone 24).

The transfer of heat from the pipe 1 occurs through the valve 1 which is exposed to the flow of refrigerant in the pipe 1 with respect to the surface in contact with this pipe.
04 and/or by adjusting the ohmic value of the resistor and/or the biasing force of the spring 17. This compensation of heat transfer from the pipe 1 to the valve 104 is particularly easy in an evaporator where the discharge pipe 1 is kept at a constant temperature, for example an evaporator producing cold water (called a chiller), and the discharge pipe l always has an outer temperature approximately equal to the temperature of the water and an inner temperature approximately equal to the temperature of the refrigerant fluid, and these temperatures are permanently held within a narrow range slightly above 0°C.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a valve used in the present invention,
A portion of this valve is shown in front" view showing the heating resistor; FIG. 2 is a diagram of a refrigeration machine using the invention; FIG. Figure 4 is a graph showing the pressure difference across the membrane as a function of the liquid content of the gas on the abscissa. Figure 4 is a graph showing the amount of valve opening as a function of the pressure difference across the membrane. Pipe, 3... Refrigerant pipe, 10... Membrane, 14... Rondo, 17... Spring, 27... Region in valve, 104... Valve. 2... Evaporator, 4 ... Container, 13... Pressure equalization line, 15... Flow rate control piston, 20... Resistor, 101... Compressor,

Claims (1)

[Claims] 1. A valve at least partially filled with liquid and connected to one side of the differential pressure measuring device, the other side of the differential pressure measuring device being exposed to the pressure of the evaporator, a pressure measuring device acting against the biasing means to control the position of the flow control means, said valve being proximate to said evaporator discharge pipe and carrying heating means, said valve being at least partially connected to said valve; A method of using a thermal expansion valve device, characterized in that the thermal expansion valve device is located within the discharge pipe. 2. The method of claim 1, wherein said valve is attached to said pipe by heat transfer insulation means. 3. The method of using a thermal expansion valve according to claim 1, characterized in that the heating means is at least partially shut off when the device is partially loaded. 4. an evaporator having a refrigerant inlet connected to a thermal expansion valve and a refrigerant discharge pipe adjacent to the valve at least partially filled with liquid; a first input connected to said valve (104); (9)
and a second input (13) exposed to the pressure inside the evaporator.
and a thermal expansion valve (104).
) comprising means (14, 17) for positioning the flow control element (15) of the valve as a function of the differential pressure measured by the differential pressure measuring means; and heating means coupled to the valve, the valve (104) comprising: An evaporator and a flow control means, characterized in that at least a part thereof is mounted in the discharge pipe (1) of the evaporator so that at least a part thereof is exposed to the flow of refrigerant in the discharge pipe. assembly. 5. Evaporator and flow control according to claim 4, wherein the valve has in the discharge pipe (1) a part (27) exposed to the flow of refrigerant and a part exposed to the heating means (20). Assembly with means. 6. An evaporator and flow control means assembly according to claim 4, wherein the bottom part of the valve (104) is inside the discharge pipe (1). 7. A refrigeration machine comprising the assembly of the evaporator and flow control means according to claim 4.