Refrigeration – Processes – Evaporation induced by sorption
Reexamination Certificate
1999-08-18
2001-04-24
McDermott, Corrine (Department: 3744)
Refrigeration
Processes
Evaporation induced by sorption
Reexamination Certificate
active
06220040
ABSTRACT:
The present invention relates to apparatus for transporting heat in general, and in particular to such apparatus having improved efficiency.
It also relates to a refrigerant for such an apparatus.
BACKGROUND OF THE INVENTION
Currently compressor driven heat pumps are mainly used for heating of e.g. houses and hot tap water. The characterizing feature of such a heat pump is that a liquid boils in the evaporator, whereby heat is taken up at low temperature and low pressure. The compressor pumps the gas from the evaporator into the condenser. In the condenser the gas is condensed to liquid, whereby heat is released at high temperature and high pressure. The liquid is returned to the evaporator via a restriction device.
However, the efficiency of the compressor is strongly dependent on the pressure difference across it, in the sense that the efficiency decreases drastically with increased pressure difference over the compressor.
A heat factor, F, of a heat pump is defined as the ratio between the heat delivered by the heat pump and the operating energy supplied to the heat pump. A normal yearly average of this heat factor for one compression-evaporation cycle is 2-2.5.
One way of increasing the heat factor is to lower the pressure difference across the compressor. This can be achieved by using a two component refrigerant, where one component comprises a gas being absorbed by the other component, which comprises a liquid.
A process utilizing such a two component refrigerant is operated as follows.
In the desorbator gas is released from the liquid, whereby heat is taken up at a low temperature and at a pressure corresponding to the concentration in the desorbator. The gas is pumped off by the compressor into the absorbator, where it again is absorbed by the liquid. In this process heat is released at high temperature and a pressure corresponding to the temperature and the concentration in the absorbator.
The liquid in the absorbator must not to be saturated with gas, because it would increase the pressure excessively in the absorbator, which of course is undesirable. Also the liquid in the desorbator must not be depleted of gas, because this would decrease the pressure in the desorbator too much. These two effects would cause the pressure difference across the compressor to increase. In order to prevent this to happen, liquid is pumped off by a liquid pump from the desorbator to the absorbator via a countercurrent heat exchanger. To prevent all liquid from collecting in the absorbator, liquid is drawn off via the heat exchanger and a restriction means from the absorbator to the desorbator. This is an entirely closed circulation system.
The two component refrigerant that is used is ammonia-water.
In DE-530 406 there is disclosed a method of generating cold comprising a compression refrigerating machine, operating with the ammonia-water system, wherein the compressor has been placed in the absorption liquid, in order to reduce noise, and to obtain improved cooling. Furthermore, in the disclosed device the condenser is also located within he absorption liquid, which is said to improve performance.
In SU-548005 there is disclosed a two-stage absorption compression refrigeration unit, wherein the compressor is placed inside the generator for cooling purposes, thereby improving economy.
In DE-31 29 957 there is disclosed a refrigerating machine operating with e.g. ammonia-water, and wherein the compressor has been integrated in the absorber unit.
A problem with prior art devices as discussed above, and the commercial heat pumps of today is the economy. The Carnot-efficiency is far from the optimum, and even very small improvements in this efficiency, say by 1-3%, require that substantial investments in improvements would have to made, and the equipment would therefore be too expensive to be commercially viable.
Another technical problem with the refrigerant system ammonia-water is its corrosive nature. Electrical and mechanical equipment such as pumps, and compressors and associated motors, will be subjected to an aggressive environment, and their operative life may be unduly shortened.
A drawback with current heat pumps is the necessity to cool the compressors. This is normally achieved by flowing air, but it often happens that temperatures in the vicinity of 100° C. and above are reached, which may lead to so called coking of the lubricant in the compressor.
SUMMARY OF THE INVENTION
The present invention therefore sets out to provide a heat transport apparatus, and in particular an improved heat pump system with increased efficiency, and wherein the disadvantages mentioned above are overcome.
This is achieved in accordance with the invention, with a heat transport apparatus as defined in claim
1
, by using a refrigerant in the form of a two component medium comprising a lubricant as the liquid component.
For the purpose of this application, “lubricant” means any compound, substance or composition meeting the criteria of the invention, i.e. having the capability of absorbing a gas, and of being enough lubricious to enable lubrication of the moving components in the system according to the invention.
Preferably at least the compressor is integrated in a desorbator of the apparatus.
Suitably also the restriction means and the liquid pump are integrated in the desorbator.
The following advantages are achieved with the invention:
The compressor is efficiently cooled, which also leads to higher compressor efficiency and heat factor.
The advantages of employing a lubricant as component in the refrigerant, is that the refrigerant will be non-corrosive.
Vibrations and lubricator splashing will agitate the refrigerant, which in its turn will render the desorption in the desorbator more efficient.
The heat pump may be manufactured in an efficient way since all component parts are integrated inside the same housing (pressure vessel).
Insulation of the heat pump will be simple thereby minimizing heat losses.
Preliminary calculations show that a heat factor of 2.6-3.5 is achievable for a system of this type at the same conditions of operation as a system of ordinary construction as discussed above, which yields a heat factor of 2-2.5.
The invention will now be described in terms of preferred embodiments thereof, with reference to the attached drawing Figures.
REFERENCES:
patent: 3990264 (1976-11-01), Patnode et al.
patent: 4048810 (1977-09-01), Zeilon
patent: 4622825 (1986-11-01), Larue et al.
patent: 4707996 (1987-11-01), Vobach
patent: 4724679 (1988-02-01), Radermacher
patent: 530406 (1933-11-01), None
patent: 1125956 (1962-03-01), None
patent: 419479 (1981-08-01), None
patent: 3100019 (1982-09-01), None
patent: 3129957 (1983-02-01), None
patent: 2102550 (1983-02-01), None
patent: 548005 (1977-11-01), None
Sjöblom Anders
Sjoblom Hans
Drake Malik N.
McDermott Corrine
Young & Thompson
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