Refrigeration – Atmosphere and sorbent contacting type
Reexamination Certificate
2001-09-14
2002-12-17
Jiang, Chen-Wen (Department: 3744)
Refrigeration
Atmosphere and sorbent contacting type
C062S094000
Reexamination Certificate
active
06494053
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related to the field of environmental control systems and more particularly, to the field of systems which combine dehumidification and air conditioning.
BACKGROUND OF THE INVENTION
In general, air conditioning systems not only reduce the temperature of the ambient air, but also remove substantial amounts of water from it. This is especially true when the air conditioner is treating “fresh” air inputted from outside the controlled environment. However, such combined air conditioning/dehumidification is generally inefficient. Furthermore, since some of the potential cooling power of the air-conditioner is used for dehumidification, the effective cooling capacity of the air conditioner is significantly reduced.
It is known in the art to provide dehumidification of air prior to its being cooled. In some cases, the mechanisms of the dehumidifier and the air conditioner are not integrated. In such cases, while there is an increase in the cooling capacity of the air conditioner, the overall efficiency of the system is relatively poor.
U.S. Pat. No. 4,984,434 describes an integrated system in which air to be cooled is first dehumidified by passing it through a desiccant type dehumidifier before being cooled by contact with an evaporator of an air conditioner. Regeneration of the desiccant is performed by passing the water containing desiccant over the condenser of the air conditioning system.
This system suffers from a number of limitations. Firstly, it dehumidifies all of the air being cooled. Since most of the air inputted to the dehumidifier is from the controlled space (and thus fairly dry already) the dehumidifier does not remove much water from the air and thus does not provide much cooling for the condenser. This would cause an overall increase in the temperature of the desiccant and a reduction in the efficiency of both the dehumidifier and the air-conditioner. A second problem is that such a system is not modular, namely, the dehumidifier must be supplied as part of the system. Furthermore, adding a dehumidifier to an existing air conditioning system and integrating the dehumidifier and air conditioner to form the system of this patent appears to be impossible.
Another type of dehumidifying/air conditioning system is also known. In this type of system, as described, for example in U.S. Pat. Nos. 5,826,641, 4,180,985 and 5,791,153, a dry desiccant is placed in the air input of the air-conditioner to dry the input air before it is cooled. Waste heat (in the form of the exhaust air from the condenser) from the air conditioner is then brought into contact with the desiccant that has absorbed moisture from the input air in order to dry the desiccant. However, due to the relatively low temperature of the air exiting the air conditioner, the amount of drying available from the desiccant is relatively low.
The above referenced U.S. Pat. No. 4,180,985 also describes a system using liquid desiccant as the drying medium for the dehumidifying system. Here again, the low temperature of the exhaust as from the air conditioner reduces substantially the efficiency of the system.
Prior art desiccant based dehumidifiers generally require the movement of the desiccant from a first region in which it absorbs moisture to a second regeneration region. In the case of solid desiccants, this transfer is achieved by physically moving the desiccant from a dehumidifying station to a regeneration station, for example by mounting the desiccant on a rotating wheel, a belt or the like. In liquid desiccant systems two pumps are generally provided, one for pumping the liquid to the regeneration station and the other for pumping the liquid from the regeneration station to the dehumidifying station. In some embodiments, a single pump is used to pump from one station to the other, with the return flow being gravity fed.
The operation of standard air conditioning systems and the desiccant systems described above is illustrated with the aid of FIG.
1
.
FIG. 1
shows a chart of temperature vs. absolute humidity in which iso-enthalpy and iso-relative humidity curves are superimposed. Normal air conditioners operate on the principle of cooling the input air by passing it over cooling coils. Assuming that the starting air conditions are at the spot marked with an X, the air is first cooled (curve 1) until its relative humidity is 100% at which point further cooling is associated with condensation of moisture in the air. In order for there to be removal of liquid from the air, it must be cooled to a temperature that is well below a comfort zone
4
. The air is heated to bring it to the comfort zone, generally by mixing it with warmer air already in the space being cooled. This excess cooling in order to achieve dehumidification is a major cause of low efficiency in such systems, under certain conditions.
Normal dehumidifier systems actually heat the air while they remove air from it. During dehumidification (curve 2) the enthalpy hardly changes, since there is no removal of heat from the system of air/desiccant. This results in an increase in temperature of both the desiccant and the air being dried. This extra heat must then be removed by the air conditioning system, lowering its efficiency.
In all dehumidifier systems mechanical power must be exerted to transfer the desiccant in at least one direction between a regenerating section and a dehumidifying section thereof. For liquid systems, pumps are provided to pump liquid in both directions between the two sections or between reservoirs in the two sections. While such pumping appears to be necessary in order to transfer moisture and/or desiccant ions between the two sections, the transfer is accompanied by undesirable heat transfer as well.
SUMMARY OF THE INVENTION
An aspect of some preferred embodiments of the invention is concerned with a combined dehumidifier/air conditioner is which a relatively low level of integration is provided. In preferred embodiments of the invention, heat generated by the condenser is used to remove liquid from the desiccant. However, unlike the above referenced prior art, the air conditioner condenser continues to be cooled by outside air. The heated air which exits the air-conditioner, containing waste heat, is used to remove moisture from the desiccant.
In contrast to the prior art, in which the heated air is the sole source of energy for the regeneration of the desiccant, in preferred embodiments of the invention, a heat pump is utilized to transfer energy from relatively cool desiccant to heat the desiccant during regeneration, in addition to the heat supplied from the exhaust of the air conditioning portion of the system. This results in a system in which the air conditioner does not have to overcool the air to remove moisture and the dehumidifier does not heat the air in order to remove moisture. This is in contrast with the prior art systems in which one or the other of these inefficient steps must be performed.
In some preferred embodiments of the invention combined dehumidifier/air-conditioner in which only “fresh”, untreated air is subject to dehumidification prior to cooling by the air conditioner. This allows for both the dehumidifier and the air-conditioner to operate at high efficiency, since the dehumidifier will be operating on only wet “fresh” air and the air conditioner will be cooling only relatively dry air.
Thus, in preferred embodiments of the invention, the amount of waste heat generated by the air-conditioner is relatively high and the heat requirements of the dehumidifier are relatively low, since a major portion of the heat for regeneration is supplied by the heat pump.
According to an aspect of the invention a simple method of integration of an air conditioner and dehumidifier is provided. In accordance with a preferred embodiment of the invention, the air conditioner and dehumidifier are separate units without conduits for air connecting the units. However, unlike prior art unintegrated units, the present invention provides advantages of utilizing waste heat f
Forkosh Dan
Forkosh Mordechai
Forkosh Tomy
Drykor Ltd.
Fenster & Company Patent Attorneys Ltd.
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