Cycle heat pump

Winter heating items fitted within room air-conditioners may be electric resistance elements, hot water or steam coils, or reverse cycle (heat pump). One model of water-cooled unit operates with a condenser water temperature high enough to be used also in the heating coil. 

Desorphon technology has been developed primarily for absorption-cycle heat pumps. The counter flow falling film absorber developed by Garimella has been tested by Determan as a desorber, requiring only modification of the flow distribution and enclosure [259]. The desorber (18 X 18 X 51 cm) could transfer... 

Fig. 7.21 Conventional vapor compression cycle heat pump (left) compared with absorption cycle heat pump (right).

In absorption cycle heat pumps, the compressor is replaced by a smaller pump and an absorption/desorption loop, greatly reducing the necessary power for moving the refrigerant through the system [256]. 

Plate-fin exchangers are widely used in electric power plants (gas turbine, steam, nuclear, fuel cell), propulsive power plants (automobile, truck, airplane), thermodynamic cycles (heat pump, refrigeration), and in electronics, cryogenics, gas-liquefaction, air-conditioning, and waste heat recovery systems. 

Nassikas AA, Akritidis CB, Mujumdar AS. Close-cycle heat pump dryer using superheated steam An apphcation to paper drying. In Mujumdar AS, ed. Drying 92. Amsterdam Elsevier Science Pubhshers, 1992, pp 1085-1098. 

Another popular heat pump concept, if not widely adopted, is the direct use of the overhead vapor as the heat pump working fluid, an open cycle heat pump termed mechanical vapor recompression (MVR). In MVR the compressor raises the pressure of the overhead vapor to the point where it will condense at a temperature sufficient to drive the reboiler. This has the advantage that the reboiler heat exchanger serves as both the reboiler and the condenser. One disadvantage is the process vapor may not be the most efficient working fluid for the temperatures involved. Nevertheless, primary energy savings over 50% are anticipated [21]. 

Figure 1.6 The Rotex absorption cycle heat pump. 

Dr Coney (1971) researched Taylor vortex flow with particular interest in rotary heat exchangers, which he later used in a rotary vapour compression cycle heat pump. Taylor-Couette flows are used in commercial intensified reactors now (see Chapter 5). 

Absorption cycle heat pumps and chillers tend to be physically large (they are essentially a collection of heat exchangers), and in the process industry applications these are invariably shell and tube units. While pressure is on the manufacturers of units for such applications to reduce their physical size, the importance of compactness... 

There are two major types of VOCs recovery refrigerated condensation (Stone 1997) and adsorption, followed by refrigeration (Hussey and Gupta 1997, Kent 1999). Although there are several types of condensation systems the most common adopted is a reverse Rankine cycle where a closed-cycle heat pump with a separate working fluid is used to condense VOCs. Adsorption is a process whereby the VOCs in the air stream are captured physically on the surface of a solid such as carbon. Steam or inert gas is... 

Figure 36.48 shows the layout of a heat-pump dehumidifying kiln. Moist air is drawn over the evaporator and condenser consecutively in a Rankine cycle heat pump. Besides these basic elements such as an evaporator, a condenser with its associated compressor, and expansion valve, there is an accumulator that prevents the refrigerant from entering and damaging the compressor and a subcooling heat exchanger to enhance the effectiveness of the heat pump. 

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