Heat pump system
Heat pump system adapted to use a non-azeotropic refrigerant mixture preferably containing a high boiling temperature refrigerant as a primary component thereof is given an improved heat transfer efficiency and its pressure loss is minimized by arranging a refrigerant extracting means for removing the refrigerant stagnating in the system in an unfavorable state, in a vapor state in a condenser or in liquid state in an evaporator and returning the removed refrigerant into a refrigerant circulating passage of the system; and by constructing an evaporator of a flooded type at least at a portion adjacent to a refrigerant outlet portion of the evaporator.
Recently, utilization of non-azeotropic refrigerant mixtures has been introduced in order to improve the coefficient of performance (COP) of heat pumps. In cases where a non-azeotropic refrigerant mixture is used in a heat pump, a counter-flow type evaporator has usually been employed so as to make the best use of the characteristics of the non-azeotropic mixture. Also, as the non-azeotropic mixture, a mixture containing a relatively larger molar fraction of a low boiling temperature refrigerant than that of a high boiling temperature refrigerant has been used.
However, in certain cases, such as a heat pump system employing, for example, a centrifugal-compressor, it is preferable to use a refrigerant having a certain degree of specific volume and therefore, it has been desired to use a refrigerant mixture containing a high boiling temperature refrigerant as a primary component. However, if a non-azeotropic mixture containing a larger molar fraction of a high boiling temperature refrigerant is used in a heat pump system, a high speed flow of a refrigerant vapor having a large specific volume is induced in the evaporator causing a pressure loss which leads to a power loss.
Also, use of a non-azeotropic refrigerant mixture naturally causes difference in respect of vaporization of the respective components as a result of which a certain component of the refrigerant mixture may stagnate within the system which may reduce the efficiency of the system.
More particularly, in an evaporator, a mixture in liquid state containing a relatively high percentage of a high temperature boiling refrigerant is likely to stay at an outlet portion of the evaporator so that heat transfer in the evaporator is impeded compared to the case where a single refrigerant is used. Or, in a condenser, an uncondensed refrigerant mixture which is rich in respect of a low boiling temperature component is likely to stay at a portion adjacent to a refrigerant outlet, thus reducing heat transfer efficiency.
Accordingly, there has been a demand for a heat pump system wherein a non-azeotropic refrigerant is effectively utilized.
As to the term “a flooded type at least at a portion adjacent to an outlet”, this refers to an evaporator structure in which flow directions of a heat source fluid and a heat sink fluid are not counter to each other and an evaporated vapor i able to flow upwards at that portion. The nature of the flooded type evaporator will be further clarified later in connection with the accompanying drawings.
The above and further objects and advantages of the present invention will be made clear when the detailed description of the invention is reviewed referring to the accompanying drawings, the brief explanation of which follows hereunder.
The term “heat pump” or “heat pump system” used throughout the present specification and claims is meant to identify a system generally comprising a compressor, a condenser, a throttle valve or a pressure reduction means, an evaporator and a refrigerant circulating passage for coupling the above elements to conduct the refrigerant through the system and such heat pump system is to be broadly interpreted to cover a heat pump system effecting a heat pump cycle not only for warming a fluid but also for cooling a fluid.
Processing your request, Please wait....
