The invention relates to a sorption cooling system, wherein heat is used to make cold. The invention relates in particular to a sorption cooling system comprising: - at least one reactor which is provided with a sorbent, a refrigerant and a heat exchange line extending through the sorbent and the refrigerant in the reactor, which reactor is embodied for alternately carrying out adsorption and desorption of the sorbent in the reactor,

- a condenser, - an evaporator,

- vapour conduits extending between the reactor and the condenser and between the evaporator and the reactor, which vapour conduits each comprise a self-acting vapour valve, which vapour valves are each provided with a passage opening, a valve seat and a valve member which is displaceable between an open position and a closed position by means of a difference in pressure between an upstream side and a downstream side of the passage opening, which valve member allows, in the open position, vapour to flow through the passage opening from the upstream side to the downstream side and rests, in the closed position, against the valve seat for closing off the passage opening in a substantially vapour-tight manner.

An adsorption cooling system is known from US 4,881,376. This adsorption cooling system comprises two adsorption columns in which a sorbent with bound refrigerant is received. Each adsorption column is connected to a condenser and an evaporator by means of vapour channels, hi addition, the evaporator and the condenser are connected to each other to form a refrigerant circuit. The adsorbent can be formed by silica gel.

A heat exchange line of a coolant circuit is attached in each adsorption column. The coolant circuit is connected via a line system with open-close valves to a warming water inlet, which is connected to a heat source, and to a cooling water inlet. This allows warm and cool water to be alternately supplied to the heat exchange lines in the adsorption columns. The heat source is for example residual heat.

This adsorption cooling system carries out a batching process. Firstly, the silica gel with bound refrigerant in one adsorption column is warmeα up oy warm water, ine warm water originates from the heat source. During this warming-up, the pressure gradually increases until the vapour tension above the silica gel is higher than the vapour tension at the condenser temperature. Subsequently, refrigerant from the silica gel will flow to the condenser and continue to warm up the silica gel while emitting vaporous refrigerant until the silica gel still contains just a small amount of refrigerant.

At the same time, the temperature of the silica gel in the other adsorption column is reduced by passing cool water through the heat exchange line of said adsorption column. The pressure drops in the process and vaporous refrigerant originating from the evaporator is absorbed in the silica gel. Vaporous refrigerant continues to be absorbed until the silica gel in said adsorption column contains a specific amount of bound refrigerant.

Afterwards, the silica gel from this last adsorption column can be warmed up, while the silica gel from the aforementioned adsorption column is cooled. In each adsorption column, there is thus a heating phase in which the silica gel is regenerated and wherein no cold is produced. Cold is made merely when the silica gel cools down and water vapour is drawn out of the evaporator. By operating the two adsorption columns in phase opposition, this adsorption cooling system can make cold continuously. For example, water flows through a heat exchange line of the evaporator, so that the temperature of the water decreases and cold water is produced.

This adsorption cooling system is in fact driven by the rise in pressure of the refrigerant as a consequence of the rise in temperature of the silica gel. The term "thermal compression" is therefore used in order to indicate that the difference in pressure that is required in order to induce condensation and evaporation during adsorption cooling is not provided by a mechanical compressor.

Butterfly valves are attached in the vapour channels between the adsorption columns and the condenser and the evaporator. In these butterfly valves, a valve disc tilts about a transverse axis, so that the valve disc comes to rest against the valve seat partially from the upstream side and partially from the downstream side. The butterfly valves each have gaskets which are attached to the valve seat, thus preventing vapour irom ieaκmg in the closed position. However, these butterfly valves are relatively heavy and expensive and take up considerable overall space.

An object of the invention is to provide an improved sorption cooling system.

According to the invention, this object is achieved in that the valve member of each vapour valve is substantially flexible, the valve member being embodied for displacement from the closed position to the open position under the influence of a difference in pressure between the upstream side and the downstream side that is less than 20 mbar, preferably less than 10 mbar, such as less than 5 mbar or less than 1 mbar. The flexible valve member prevents vapour from leaking substantially completely in the closed position. The displaceable valve member can close off the vapour valve in a substantially vapour-tight manner without using a separate seal. At the same time, the vapour valve is light, compact, inexpensive and reliable. Surprisingly, the vapour valve according to the invention also provides optimum timing for opening and closing of the vapour conduit of the sorption cooling system. The flexibility of the valve member is determined by the selection of the material thereof (for example silicone rubber, natural rubber, etc.), the dimensions (such as the thickness of the material) and shape (for example in the shape of a hemisphere).

In one embodiment, the refrigerant is water or methanol. In the sorption cooling systems using water or methanol as the refrigerant, very low pressure differences occur, as a result of which the embodiments of the present invention wherein the valve member operates reliably at these low pressure differences can advantageously be used.

In one embodiment, the valve seat is substantially rigid. As a result, the flexible valve member ensures that the passage opening of the vapour valve is sealed to the rigid valve seat in the closed position. The rigid valve seat is for example made of metal, such as aluminium. In the closed position, the flexible valve member prevents vaporous refrigerant from being able to leak through the passage opening.

It is possible for the valve member to comprise a flexible suction cup which is provided with a sealing edge, the sealing edge of the suction cup rc&uug agamsi me vaivc ∞ai m the closed position. A valve member embodied as a suction cup is particularly simple and inexpensive. The sealing edge is for example formed by the leading circumferential edge of the suction cup, which faces the valve seat. In the closed position, said circumferential edge is pressed against the valve seat, thus forming a seal which is substantially leak-tight to the vaporous refrigerant.

In one embodiment, the valve member comprises a flexible sealing member having an outer surface, wherein, in the closed position, the flexible sealing member is partially accommodated in the passage opening and the outer surface rests against the valve seat and wherein, in the open position, an opening is left free between the outer surface and the passage opening. For example, the flexible sealing member is formed as a flexible sphere having a diameter which is larger than the diameter of the passage opening, and the flexible sphere, in the closed position, being partially accommodated in the passage opening and producing a seal against the valve seat with the outer surface. The passage opening can be embodied as a conical channel.

In one embodiment, the valve member is substantially rectilinearly displaceable between the open position and the closed position. The valve member comprises, for example, a straight guide rod for guiding the rectilinear displacement of the valve member between the open and closed positions. During the displacement between the opened and closed positions, the valve member performs a translational movement. A translational movement for opening and closing the vapour valve allows a simple design of the vapour valve.

Instead of being rectilinearly displaceable, the valve member can be hingeable between the open position and the closed position. The hinge axis is in this case located laterally with respect to the passage opening. The valve member does not tilt through the passage surface, but hinges above the passage surface upward and downward with respect to the valve seat. As a result, the passage opening is reliably sealed in the closed position.

In one embodiment, the valve member is attached within the vapour conduit in such a way that gravity operates toward the closed position Oi me vaivc mcmocr. HI υuicr words, the valve member is located above the valve seat. The valve member falls, under the influence of the dead weight thereof, back to the closed position, unless the pressure difference over the valve member generates a lifting force which is greater than the weight of the valve member. The valve member is then raised to the open position.

It is also possible for the valve member to be biased to the closed position by a spring means. The spring means can be slid onto a guide rod for guiding a rectilinear displacement of the valve member. The spring means ensures that the vapour valve remains closed unless the pressure difference over the valve member is sufficiently great to overcome the spring force of the spring means and/or the weight of the valve member.

In one embodiment, the valve member is embodied for displacement from the closed position to the open position under the influence of a difference in pressure between the upstream side and the downstream side that is less than 20 mbar, preferably less than 10 mbar, such as less than 5 mbar or less than 1 mbar. A vacuum can prevail in the sorption cooling system during operation. A low absolute pressure, which is for example between 0.1 and 60 mbar, prevails in the reactor, the condenser and the evaporator of the sorption cooling system. The vapour valves according to the invention are particularly suitable for switching between the open and closed positions at such low pressure and minor pressure differences, hi other words, the vapour valve according to the invention is highly sensitive.

In one embodiment, the vapour valve comprises actuating means for actuating the valve member to the closed position and/or the open position. This enables the sorption cooling system to store cold when the sorption cooling system is temporarily not in use. In order to store cold, the sorbent is firstly regenerated in the reactor, i.e. substantially completely evaporated. Subsequently, the actuating means keep the vapour valve between the evaporator and the reactor closed, so that no vapour can flow from the evaporator to the reactor. The actuating means prevent the occurrence of gradual adsorption of the sorbent in the reactor. When the sorption cooling system is subsequently switched on, cold is immediately available.

The invention also relates to a vapour valve for use in a sorption cooling system as described hereinbefore.

The invention will now be commented on in greater detail with reference to the appended drawings, in which:

Figure 1 is a process diagram of a first embodiment of a sorption cooling system according to the invention;

Figure 2 is a process diagram of a second embodiment of a sorption cooling system according to the invention;

Figures 3a, 3b, 3c show a first embodiment of a self-acting vapour valve for use in the sorption cooling system shown in Figure 1 or 2;

Figure 4 shows a test arrangement used to test characteristic properties of the present vapour valve; and

Figure 5 is a cross-sectional view of a further embodiment of a vapour valve.

The sorption cooling system 1 shown in Figure 1 comprises a reactor 3, a condenser 10, an evaporator 18, a heat source 26, a heat emitter 28 and a valve system 30. The sorption cooling system 1 uses heat from the heat source 26 to make cold.

A sorbent with bound refrigerant is received in the reactor 3. In this exemplary embodiment, the sorbent is silica gel and the refrigerant is water. Silica gel is highly hygroscopic, i.e. attracts water. In the completely saturated state, silica gel can absorb approximately 35 per cent by weight of water. Other combinations of sorbent and refrigerant are of course also possible. The reactor 3 has a supply 4 for supplying water vapour from the evaporator 18 and a discharge 5 for discharging water vapour to the condenser 10. A heat exchange line 8 extends through the silica gel with bound water in the reactor 3. The heat exchange line 8 is connected to me vaivc jtysiciπ JU.

The condenser 10 comprises a supply 11 for supplying water vapour from the reactor 3. The discharge 5 of the reactor 3 and the supply 11 of the condenser 10 are connected to each other by a vapour conduit 92. A self-acting vapour valve 96 is attached in the vapour conduit 92. The condenser 10 is provided with a heat exchange line 15 for conveying cool liquid, such as cooling water. In the condenser 10, the supplied water vapour condenses, after which the water (condensate) leaves the condenser 10 via a discharge 12.

The discharge 12 of the condenser 10 is connected to a supply 19 of the evaporator 18 via a return line 90. A condensate valve 91 is attached in the return line 90. The evaporator 18 comprises a heat exchange line 23 through which a fluid, such as water, flows. This fluid transfers heat to the water (condensate) supplied via the supply 19. This produces water vapour which leaves the evaporator 18 via a discharge 20. The water vapour flows back to the supply 4 of the reactor 3 via a vapour conduit 93. A self-acting vapour valve 96 is also attached in the vapour conduit 93 between the discharge 20 of the evaporator 18 and the supply 4 of the reactor 3.

The cooling using the sorption cooling system 1 operates in accordance with a batching process - the reactor 3 is embodied for alternately carrying out adsorption and desorption of the sorbent in the reactor 3. Firstly, the silica gel in the reactor 3 contains, for example, approximately 10 per cent of bound water, while the temperature is approximately 30 ⁰ C, Since the refrigerant circuit contains no gases other than the water vapour, the pressure is caused by the water vapour tension. Warming up the silica gel causes the pressure to gradually increase until the water vapour tension above the silica gel is higher than the vapour tension at the temperature in the condenser 10. The pressure in the reactor 3 rises for example to 60 mbar, while the pressure in the condenser 10 is 50 mbar. Water vapour will now flow to the condenser 10 via the self- acting vapour valve 96 and continue to warm up the silica gel in the reactor 3 while emitting water vapour (desorption). hi practice, the pressure difference over the vapour valve 96 is very low when water or methanol is used as the refrigerant (order of magnitude of from 1 mbar to a few tens of mbar). When the silica gel contains for example just 3 per cent of bound water, the silica gel is subsequently cooled down. The pressure drops in this case to a pressure which is lower than the pressure in the evaporator 18. Water vapour originating from the evaporator 10 flows via the self-acting vapour valve 96 to the reactor 3 and is absorbed in the silica gel (adsorption). Water continues to be absorbed until the silica gel contains again, for example, approximately 10 per cent of bound water at a temperature of approximately 30 ⁰ C.

In the sorption cooling system 1 according to Figure 1, in the cooling-down phase of the silica gel in the reactor 3, water vapour is drawn out of the evaporator 18 and the water (condensate) supplied via the supply 19 evaporates in the evaporator 18. In this case, heat is withdrawn from the cold fluid flowing through the heat exchange line 23 of the evaporator, i.e. the temperature of the cold fluid falls. The temperature of the cold fluid is below the ambient temperature, for example between 5 and 15 ⁰ C, such as 10 ⁰ C. The cold fluid, such as cold water, forms the cold product of the sorption cooling system 1.

The refrigerant - in this exemplary embodiment water/water vapour - circulates in a refrigerant circuit of the sorption cooling system 1. A coolant circuit is provided to alternately cool and heat the reactor 3 with the silica gel and water bound thereto. The coolant circuit comprises the valve system 30, the heat source 26 and the heat emitter 28. The valve system 30 is embodied for alternately supplying warm water and cool water to the reactor 3.

A second embodiment of a sorption cooling system according to the invention is represented in Figure 2. Like or similar components are indicated therein by like reference numerals. The sorption cooling system 1 shown in Figure 2 comprises a second reactor 73 which is filled with silica gel and water bound thereto. Just like the reactor 3, the second reactor 73 comprises a supply 74 and a discharge 75 for water vapour. A heat exchange line 78 extends through the silica gel in the second reactor 73.

The condenser 10 comprises a second supply 16 which is connected to the discharge 75 of the second reactor 73 via a vapour conduit 94. A sen-acung vapour vaive sro is attached in the vapour conduit 94 between the second supply 16 of the condenser 10 and the discharge 75 of the second reactor 73. Condensation of water vapour in the condenser 10 produces water (condensate) which flows out of the condenser 10 via the discharge 12. The water (condensate) is supplied to the supply 19 of the evaporator 18 via the return line 90 and the condensate valve 91.

In the evaporator 18, the water (condensate) supplied via the supply 19 can evaporate by having a fluid flow through the heat exchange line 23. The evaporator 18 has a second discharge 25 for discharging water vapour. The second discharge 25 is connected to the supply 74 of the second reactor 73 by means of a vapour conduit 95. A self-acting vapour valve 96 is attached in the vapour conduit 95.

The sorption cooling system shown in Figure 2 has a second refrigerant circuit in which the refrigerant - in this exemplary embodiment water/water vapour - can circulate. The functioning of the sorption cooling using the second refrigerant circuit of the second reactor 73 is the same as that described hereinbefore with reference to the first exemplary embodiment shown in Figure 1. The batching processes in the first and second refrigerant circuit are operated, in the sorption cooling system shown in Figure 2, in phase opposition in order to continuously produce cold.

The self-acting vapour valves 96, which are attached in each vapour conduit 92, 93, 94, 95 of the sorption cooling system according to Figure 1 or 2, are embodied as a check valve. A first embodiment of the self-acting vapour valve 96 is shown in Figures 3a, 3b and 3c. This vapour valve 96 comprises a passage opening 97 which is delimited by a valve seat 98. The passage opening 97 can be closed off in a substantially vapour-tight manner by a valve member 99 which is displaceable between a closed position shown in Figure 3a and an open position represented in Figure 3b.

In this exemplary embodiment, the valve member 99 is embodied in a flexible manner, for example by selecting silicone rubber or natural rubber as a material. The valve member 99 forms a flexible suction cup having a sealing edge 102 facing the valve seat 98. The valve seat 98 is substantially rigid - the valve seat 98 is for example made of metal, such as aluminium. In the closed position, the sealing eαge lυz is ciampeα against the valve seat 98 (see Figure 3a), so that the passage opening 97 is sealed. When the sealing edge 102 is displaced away from the valve seat 98, vapour can flow through the passage opening 97 and the space between the sealing edge 102 and the valve seat 98.

The vapour flows from the upstream side 100 to the downstream side 101 of the vapour valve 96. For a vapour valve 96 between the reactor 3, 73 and the condenser 10, the reactor 3, 73 forms the upstream side 100 and the condenser 10 is the downstream side 101. A vapour valve 96 attached in the vapour conduit 93, 95 between the evaporator 18 and the reactor 3, 73 has the evaporator 18 at the upstream side 100 and the reactor 3, 73 at the downstream side.

During displacement from the open position to the closed position, the valve member 99 comes to lie against the valve seat 98 merely from the upstream side 101. The valve seat 98 is turned in its entirety toward the downstream side 101, i.e., in the vapour conduit 92, 94 between the reactor 3, 73 and the condenser 10, toward the condenser 10 and, in the vapour conduit 93, 95 between the evaporator 18 and the reactor 3, 73, toward the reactor 3, 73. In order to close the vapour valve 96, the valve member 99 is displaced toward the valve seat 98 from one side, namely the downstream side 101.

During displacement between the closed position and the open position, the flexible suction cap 99 follows substantially a rectilinear path. This rectilinear displacement proceeds substantially along the axis of the vapour conduit 92, 93, 94, 95. For this purpose, the flexible suction cap 99 is connected to a guide rod 104 which is displaceably accommodated in a guide sleeve 106. In one embodiment (not shown in the present document), the flexible suction cap is hingeably connected to the valve seat - the flexible suction cap can tilt upward in this case.

The vapour valve 96 is arranged within the vapour conduit 92, 93, 94, 95 in such a way that gravity exerts a force on the flexible suction cap 99 with the guide rod 104 to the closed position. In this exemplary embodiment, the guide rod 104 has, at the end thereof positioned opposite the flexible suction cap 99, a stop part 105. A spring means 104 is biased between the guide sleeve 106 and the stop pan W3, so mat tne πexioie suction cap 99 is drawn toward the closed position. When the difference in pressure between the upstream side 100 and the downstream side 101 increases during adsorption and desorption of the silica gel in the reactor 3, the force exerted on the flexible suction cap 99 as a result of the pressure difference will at a given moment exceed the force exerted by gravity and the spring force. The flexible suction cap 99 then moves upward to the open position. The vapour valve is therefore displaceable as a consequence of a difference in pressure between the condenser and the reactor or between the reactor and the evaporator. This pressure difference is relatively slight, such as less than 5 or even 1 mbar. A pressure of 0.1-60 mbar, for example, prevails in the refrigerant circuit.

A vapour valve 96 as described hereinbefore and represented in Fig. 3a-3c was used to carry out tests to determine the pressure difference required to open the valve member 99 and also to determine the leakage in the closed state. In these tests, the vapour valve 96 was placed horizontally between two closed-off compartments 41 , 42 which were positioned one above the other and the absolute pressure of which could be set separately P) and P _h with the aid of a few control valves 43a-c and a pressure source 44, as illustrated in Fig. 4. Measurements were taken using a first pressure gauge 45, which measures the absolute pressure in the top compartment 41, and a second pressure gauge 46, which measures the pressure difference over the vapour valve 96. These tests revealed that opening the vapour valve 96 requires a difference in pressure of at most 0.8 mbar between the upstream side and the downstream side. In most cases, the vapour valve 96 opens at a pressure difference of just 0.4 mbar.

In addition, tests were carried out to determine the leakage rate. When the vapour valve 96 was closed, a leakage rate of from 0.1 to 0.4 mbar/second was observed at a difference in pressure between the downstream pressure less the upstream pressure of between 0 and 20 mbar. It may be concluded from these results that this vapour valve 96 is extremely suitable for use in a sorption cooling system using water or methanol as the refrigerant, as a result of the low pressure differences in the order of magnitude of a few mbar that occur in this case. The weight of the flexible suction cap 99 and the spring means IIAJ are αesigneα in such a way that the vapour valve 96 opens and closes on switching between adsorption and desorption in the reactor 3, 73. The self-acting vapour valves 96 therefore provide optimum timing for opening and closing the vapour conduits 92, 93, 94, 95 without external regulation and sensors. As a result of the low weight of the flexible suction cup 99, the vapour valve 96 rises relatively far from the closed position to the open position, so that the pressure drop over the vapour valve 96 is relatively low. The weight of the flexible valve member 99 is for example also determined by the shape (for example the curved surface shown in Fig. 3a-3c, for example in the shape of a part of a sphere, a bell shape, etc.) and the thickness of the material used (for example in the order of magnitude of at most a few millimetres). In one exemplary embodiment of the valve member 99, said valve member is embodied with a diameter of 60 mm, a height of 20 mm and a weight of 22 grammes.

The invention is not limited to the exemplary embodiments illustrated in the figures. The person skilled in the art may make various adaptations which fall within the scope of the invention.