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(11) | EP 0 059 692 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Combined refrigerator/water heater unit |
| (57) The present invention relates to a refrigerator fitted with water heating means for
collecting the heat dissipated on the condenser of the said appliance as well as means
for transferring the heated water to a cistern of a normal electric water-heater. The said collecting means consist of a coil-shaped part of the condenser itself and a storage tank full of water containing the said coil-shaped part of the condenser. The transfer means consist of two water pipes, one supply and one pick-up, between the storage tank and cistern, a "T" fitting for connecting the storage tank and cistern pick-up pipes to the hot water pipe and a water flow regulating valve for only allowing water to flow into the storage tank from the cistern and not from the water mains supply pipe, so as to prevent sharp changes in temperature on the condenser which could impair operation of the appliance as well as to prevent cold water from getting into the hot water outlet pipe. The energy collected on an appliance fitted with the said heat collecting means is equivalent to consumption for operating the appliance itself solely as a refrigerator. |
[0001] The present invention relates to a combined refrigerating/hot water device comprising a compressor for compressing the refrigerating fluid, a condenser for condensing the refrigerating fluid from the compressor, a capillary tube for expanding the refrigerating fluid from the condenser, evaporating means for evaporating the refrigerating fluid from the capillary tube and, finally, a return pipe connecting the outlet on the evaporating means to the input on the compressor. I
[0002] We all know how, particularly over the past few years, increasing need has been felt for saving on energy and how manufacturers of household appliances have attempted to meet this demand by directing research towards lower and lower consumption and devising means of collecting energy which, up to now, has always been allowed to escape. Particularly in the case of refrigeration appliances, e.g. freezers, attempts have been made to collect the heat dissipated on the condenser which would otherwise be lost.
[0003] In one solution, the condenser is placed inside a cistern of a water-heater for heating the water inside.
[0004] If the temperature of the water is considered too low, an electric resistor fitted on the cistern may be activated until the required temperature is reached, e.g. This solution presents a number of drawbacks, for example, the need for a special cistern with obvious limitations both in terms of choice by the consumer, who is compelled to buy two appliances, i.e. a freezer designed for recovering heat and a specially designed cistern, as well as in terms of the said heat collection device being used on existing, ordinary cisterns of water-heaters.
[0005] A further drawback of this solution is that the freezer and cistern must be connected by two pipes in which the refrigerating fluid flows at a pressure of usually around 10 Atm.
[0006] As both appliances are rarely in the same room or even close to each other, there is a dangerous risk of these pipes being damaged with consequent leaking of the refrigerating fluid and a break-down on the freezer.
[0007] Furthermore, as it is impossible to know the distance between the two appliances before installation, the length of the two pipes must be made adjustable. This cannot be done, however, as they form part of the refrigerating fluid circuit that must be sealed when the appliance is manufactured. Problems are therefore bound to be encountered in connection with the rigidity of the system which cannot be adapted to different installation requirements.
[0008] This problem may be overcome by using very long pipes but, besides the waste involved, it affords no improvement in rigidity.
[0009] Another drawback lies in the fact that the condenser is fully housed inside the cistern which, as we have already mentioned, is also fitted with an electric resistor. This may be kept running for a long period of time for bringing all the water inside the cistern up to 60°C. If this is the case, there can be no heat exchange by the condenser as the outside temperature is more or less the same as the fluid circulating inside it and operation of the freezer will be impaired. It is common knowledge that the efficiency of a freezer is inversely proportional to the condensation temperature of the refrigerating fluid so that any attempt to overcome the problem by raising the said condensation temperature will only worsen efficiency. In fact, with a condensation temperature of 30-35°C, performance of the said freezer is optimum with the compressor running about 50%. In the high condensation temperature solution described above, however, the compressor has to be kept running longer which means higher consumption for running the freezer with a heat collecting device than without.
[0010] The aim of the present invention is therefore to overcome the above drawbacks by providing a device for collecting the heat dissipated through the condenser on food refrigerating and/or freezer appliances, that can be connected easily and cheaply to a cistern of a normal electric water-heater though with little or no effect on the normal efficiency of the said appliances without the heat collecting feature, thus providing for considerable saving in energy.
[0011] Further aims of the present invention are to avoid having to run the high-pressure refrigerating fluid pipes from the refrigerator to the cistern and to provide simple, ordinary means for connecting the said two appliances so as to enable maximum freedom of choice as to the position and distance between the appliances and make installation of the said device as simple and fast as possible.
[0012] With these aims in view, the present invention relates to a combined refrigerating/hot water device comprising a compressor for compressing the refrigerating fluid, a condenser for condensing the refrigerating fluid from the compressor, a capillary tube for expanding the refrigerating fluid from the condenser, evaporating means for evaporating the refrigerating fluid from the capillary tube and, finally, a return pipe connecting the outlet on the evaporating means to the input on the compressor, characterised by the fact that means are provided for heating the water by collecting and storing the heat available on the condenser, the said means being connected to a tank of water by connecting means comprising a pipe, as well as means for regulating the flow of water so that cold water can only circulate from the bottom of the tank to the water heating means and the hot water only from the heating means to the top of the tank or hot water pipe.
[0013] A detailed description of the invention will now be given with reference to the attached drawings provided by way of a non-limiting example in which:
- Fig. 1 shows a cross section of a top-loading freezer, fitted with the device covered by the present invention, and a cistern cut off in the middle.
- Fig. 2 shows a cross section of a valve for regulating the flow of water from the outside mains.
[0014] With reference to Fig. 1, top-loading freezer 1 comprises compressor 2 for compressing the refrigerating fluid, condenser 3, 4 for condensing the refrigerating fluid from the compressor, capillary tube 5 for expanding the refrigerating fluid from the condenser, expanding means, not shown in the diagram, for evaporating the refrigerating fluid from capillary tube 5 and return pipe 6 connecting the outlet on the evaporating means to the input of compressor 2.
[0015] The condenser has been divided into two parts: the first, in the shape of a coil, 3, is placed inside an insulated storage tank 7 full of water while the second, 4 , is left exposed. Storage tank 7 has two 3/4" coupling marked 8 and 9 which act as an inlet and outlet for receiving and supplying water from and to cistern 13 respectively. One end of pipe 10 is fitted to coupling 8 while the other is fitted to flow regulating valve 11 which will be described in more detail later on. The other two apertures on valve 11 are connected one to input 12 of cistern 13 and the other to external cold water pipe 14. Coupling 9 is connected to one end of pipe 15 the other end of which is connected to "T" fitting 16. The other two apertures of fitting 16 are connected one to hot water outlet 17 on cistern 13 and the other to hot water pipe 18. Pipes 10 and 15 are ordinary water pipes capable of withstanding the 8 Atm pressure, the safety valves on standard cisterns are usually set to.
[0016] Moving on to Fig. 2, this shows a flow regulating valve 11 consisting of : a ½" coupling 19 the cold water from mains pipe 14 flows in through; a space 20 closed off at the bottom for allowing the cold water to flow straight into cistern 13 along inlet pipe 12; and a centre pipe 21 which is longer at the top than inlet pipe 12 and allows the water at the bottom of cistern 13 to reach inlet 8 of storage tank 7 via 3/4" coupling 22 and pipe 10.
[0018] To 'explain how the device works, we shall start by assuming the water in both cistern 13 and storage tank 7 is cold.
[0019] When compressor 2 is running, the coil part of the condenser 3 supplies the heat generated during the refrigeration cycle to the water in storage tank 7 which begins to heat up. The hot water is then thermosiphoned upwards until it eventually reaches cistern 13 via coupling 9, pipe 15, "T" fitting 16 and coupling 17. At the same time, the cold water in cistern 13 starts to move down through coupling 12, valve 11, pipe 10 and coupling 8 into storage tank 7 where it too is heated. The cycle continues in this way until all the water in cistern 13 reaches the same temperature as the water in storage tank 7.
[0020] As the water is thermosiphoned to and from storage tank 7 and cistern 13, pipes 10 and 15 must obviously be slanted so as to enable the water to circulate with no bends or siphons impeding it. It also goes without saying that cistern 13 must be placed over storage tank 7. The refrigerating circuit has been designed so that, during the operating cycle, the refrigerating fluid is first overheated and then overcooled so that at least part of coil-shaped condenser 3 is at a temperature of 70-80°C for bringing the water in storage tank 7 to a temperature of 60-70°C. The exposed room-temperature part of the condenser 4 ensures that, under any operating conditions, the condensation temperature of the refrigerating fluid is around 45-55°C. In fact, if this part of the condenser was not provided for, under certain conditions, the refrigerating fluid could not be condensed properly and operation of freezer 1 would be impaired or even stopped. This is what would happen, for example, if all the water in both cistern 13 and storage tank 7 reached such a high temperature that the difference between the outside temperature and the temperature inside coil-shaped condenser 3 is not sufficient to ensure proper heat exchange.
[0021] The size of coil-shaped condenser 3 for heating the water and exposed part 4 depends on the temperature the water is to be heated to, the condensation temperature the refrigerating fluid is used at and the efficiency required from freezer 1. If overheating or -cooling of the refrigerating fluid is to be avoided (in view of the slight fall in freezer efficiency involved), a special refrigerating fluid for operating at a condensation temperature of 70-80°C could be used.
[0022] The function of electric resistor 23 is to ensure hot water is produced even when freezer 1 is not running as well as to supply the energy needed for heating large quantities of water which the heat collecting device alone could not bring up to the required temperature.
[0023] To understand the real importance of flow regulating valve 11, imagine hot water is tapped from pipe 18. This flows from cistern 13 through "T" fitting 16 while, at the same time, cold water flows into cistern 13 via flow regulating valve 11. The water then flows from cistern 13 to storage tank 7, again through valve 11. If this was not provided for, cold water would flow under pressure into both cistern 13 and tank 7. Water in the latter could therefore be forced through pipe 15 and "T" fitting 16 into pipe 18 where it would mix with the water from cistern 13. This would occur even if the temperature of the water in tank 7 was lower than that in cistern 13 as circulation in this case depends on pressure and not on thermosiphoning.
[0024] Calculating the right length and/or section of pipe 21 is important if the water for heating in storage tank 7 is to be isolated from the cold water from the mains. If this was not so, instead of the hot water from cistern 13, pipe 18 would receive water at far below the required temperature the effect of which can be imagined.
[0025] The function of flow regulating valve 11 is therefore to isolate storage tank 7 from the main water circuit and ensure it only "communicates" with cistern 13. Another advantage of valve 11 is that it prevents sharp changes in temperature around the condenser (i.e. the water in tank 7) which provides for better sizing and more rational use of the entire refrigeration circuit.
[0026] To give a better idea of just how much energy can be saved using the present invention, let us examine the case of a 250 litre freezer designed to give a temperature of -25°C on the evaporator under the following conditions:
1) Condensation temperature 45°C Cooling capacity 125 Kcal/h Power absorption 130 W Heat from condenser 150 Kcal/h
2) Condensation temperature 55°C Cooling capacity 115 Kcal/h Power absorption 150 W Heat from condenser 138 Kcal/h
[0027] Assume the heat collecting device is used for heating the daily water requirement of a family of 4 in:
A) the bathroom
B) the kitchen
[0029] It is also assumed the freezer is run for 50% of the time and that a family of 4 requires 240 litres of water at 40°C a day, amounting to 240 x (40-10) = 7200 Kcal/24h.
[0030] Now, let us calculate the energy saved in each case on the basis of these assumptions:
1A) The condenser gets through 150 Kcal/h for 50% of the time which, over 24 hours, gives 150 x 0.5 x 24 = 1800 Kcal/24h representing 25% of the total requirement. Over 24 hours, the freezer consumes 130 x 0.5 x 24 = 1560 Wh which represents a saving of 25% on the energy needed to heat the water to 60°C with no increase in the consumption of the freezer.
2A) The condenser gets through 138 Kcal/h for 50% of the time which, over 24 hours, gives 138 x 0.5 x 24 = 1656 Kcal/24h representing 23% of the total requirement. Over 24 hours, the freezer consumes 150 x 0.5 x 24 = 1800 Wh, that is, 240 Wh more than in the previous case. As 240 Wh is equivalent to 206 Kcal, of the 1656 Kcal/24h saved, the extra 206 Kcal/24h must be subtracted to give a net saving of 1656 - 206 = 1450 Kcal/24h which represents 20% of the total requirement. In fact, the net saving on energy in this case for heating the water to 60°C is 20%.
[0031] Now, let us assume the daily water requirement in the kitchen for a family of 4 is 100 litres at 40°C, equivalent to 100 x (40-10) = 3000 Kcal/24h. •
1B) The condenser gets through 1800 Kcal/24h representing 60% of the total requirement. As in the case of 1A), there is no increase in consumption for running the freezer which amounts to an energy saving of 60%.
2B) The condenser gets through 1656 Kcal/24h representing 55% of the total requirement. In this case, however, there is an increase of 206 Kcal/ 24h in the consumption of the freezer giving an actual saving of 1450 Kcal/24h or 48% of the total requirement. In actual fact, the energy saved in this case is 48%.
[0033] In particular, the possibility of connecting the said device easily to cisterns of normal electric water-heaters requiring no alternations; the low cost and good reliability of additional parts for connecting the device to the cistern which consist of ordinary water pipes; the versatility of the said connecting parts which enable the freezer and cistern to be arranged as required; and, finally, the big saving on energy which, as shown in the examples, is always greater than the consumption of the freezer so that, whatever the hot water is used for, consumption for running the freezer fitted with the present invention is nil.
1) Combined refrigerating/hot water device comprising a compressor for compressing
the refrigerating fluid, a condenser for condensing the refrigerating fluid from the
compressor, a capillary tube for expanding the refrigerating fluid from the condenser,
evaporating means for evaporating the refrigerating fluid from the capillary tube
and, finally, a return pipe connecting the outlet on the evaporating means to the
input on the compressor, characterised by the fact that means are provided for heating
the water by collecting and storing the heat available on the condenser, the said
means being connected to a tank of water (13) by connecting means comprising a pipe,
as well as means for regulating the flow of water so that cold water can only circulate
from the bottom of the tank (13) to the water heating means (3, 7) and the hot water
only from the heating means (3, 7) to the top of the tank (13) or hot water pipe (18).
2) Combined refrigerating/hot water device comprising a compressor for compressing
the refrigerating fluid, a condenser for condensing the refrigerating fluid from the
compressor, a capillary tube for expanding the refrigerating fluid from the condenser,
evaporating means for evaporating the refrigerating fluid from the capillary tube
and, finally, a return pipe connecting the outlet on the evaporating means to the
input on the compressor, characterised by the fact that means are provided for heating
the water by collecting and storing the heat available on the condenser comprising
only the coil-shaped part of the said condenser and a storage tank (7) full of water
in which the said coil-shaped part of the condenser (3) is placed.
3) Combined refrigerating/hot water device as per Claim 2, characterised by the fact
that part of the said condenser (4) is left exposed to enable further condensation
of the refrigerating fluid over and above that afforded by the coil-shaped part of
the condenser (3) so as to ensure sufficient condensation of the refrigerating fluid
in any operating condition.
4) Combined refrigerating/hot water device as per Claim 3, characterised by the fact
that the said exposed part of the condenser (4) is sized so that, when the coil-shaped
part of the condenser (3) is unable to exchange heat because of the slight rise in
temperature between the refrigerating fluid inside and the surrounding water, it can
ensure sufficient condensation of the refrigerating fluid and operation of the said
device for producing cold.
5) Combined refrigerating/hot water device as per Claims 1 and 2, characterised by
the fact that the refrigerating fluid is specially selected for operating at a condensation
temperature higher than the maximum temperature settled for the water contained in
the tank (13), so as to heat the water in the said storage tank (7) to a temperature
higher than the said settled maximum with no substantial reduction in the efficiency
of the said device.
6) Combined refrigerating/hot water device as per Claims 1 and 2, characterised by
the fact that the said means for connecting the storage tank (7) and water tank (13)
comprise two threaded couplings (8,9), two water pipes (10, 15) of adjustable length,
a "T" fitting (16) and flow regulating valve (11).
7) Combined refrigerating/hot water device as per Claim 1, characterised by the fact
that the said flow regulating means at the cold water inlet end comprise a flow regulating
valve (11) with an inlet (19) and two outlets, the first outlet (12, 20) allowing
the cold water received at inlet 19 to flow through directly and the second (21, 22)
allowing the cold water received at inlet 19 to flow through indirectly.
8) Combined refrigerating/hot water device as per Claim 7, characterised by the fact
that, on the said flow regulating valve (11), the said inlet essentially comprises
a first pipe with a threaded coupling (19), the said first outlet essentially comprises
a second pipe with a threaded coupling (20) connected directly to the said first pipe
while the said second outlet essentially consists of a pick-up pipe (21) inserted
into the said bottom part of the water tank (13) with a threaded end by which it is
connected to the said water heating means (7) via the said connecting means (9).
9) Combined refrigerating/hot water device as per Claim 8, characterised by the fact
that the said pick-up pipe (21) is at least partly fitted inside the said second pipe
and that means are provided to prevent cold water from flowing directly from the said
inlet to the said second outlet.
10) Combined refrigerating/hot water device as per Claim 8, characterised by the fact
that at least part of the said pick-up pipe (21) may be made of flexible plastic capable
of withstanding operating temperature.
11) Combined refrigerating/hot water device as per Claim 1, characterised by the fact
that the said flow regulating means are sized to prevent sharp changes in the temperature
of the water in the said water heating means during operation of the device.
12) Combined refrigerating/hot water device as per Claim 2, characterised by the fact
that the refrigerating circuit is sized so that the average temperature at which the
said refrigerating fluid condenses is a compromise between the need to produce a sufficiently
high temperature in the said water heating means for the water to be used and the
need to maintain good efficiency of the cold producing device.
13) Combined refrigerating/hot water device as per Claim 12, characterised by the
fact that the said average condensation temperature is about 45°C.
14) Combined refrigerating/hot water device as described and shown in the attached
diagrams.