Evaporators heat pump

Figure 22.5 shows the grand composite curve for this process and the location of the evaporator heat pump. The... 

Heat Pumps. A heat pump is a refrigeration system that raises heat to a useful level. The most common appHcation is the vapor recompression system for evaporation (qv) (Fig. 14). Its appHcation hinges primarily on low cost power relative to the alternative heating media. If electricity price per unit energy is less than 1.5 times the cost of the heating medium, it merits a close look. This tends to occur when electricity is generated from a cheaper fuel (coal) or when hydroelectric power is available. 

C 0.35 Recovery of low level waste heat f space heating, district heating syste Absorption cooling. Recovery of steam condensate and flash steam. Heat pump for evaporation, drying, etc. 3r m. 

The cycle consists of two phases. In the first, suppose pumping to be anticlockwise, and initially that bed 1 is cold (maximum adsorbent concentration) and bed 2 is hot (minimum adsorbent concentration). The oil recovers heat from bed 2, has a further heat addition from the gas heat exchanger and then proceeds to heat bed 1 via the special heat exchanger within it. Bed 1 desorbs refrigerant which passes to the condenser (giving a useful heat output in the case of a heat pump) and bed 2 adsorbs gas from the evaporator which... 

Some heat pumps, such as the dehumidifier, serve the double purpose of a useful load both on the evaporator and condenser side. Again, there is no reversal of the refrigerant flow in operation so the components maybe selected without compromise. 

Evaporators for heat pumps are designed for a low temperature difference, to get the best COP from a given heat source, so they... 

Air conditioners are frequently combined with heaters. A convenient place must be found for the compressor, generally outdoors. Heat pumps have been used a great deal in recent years with satisfactory results. In very dry climates, laboratories often install evaporative coolers because of their reasonable cost of installation and operation. Their one drawback, sometimes serious, is that the inside air tends to become uncomfortably humid. 

Heat pumps are increasingly finding applications in the process industries. A typical application is the use of the low grade heat from the condenser of a distillation column to provide heat for the reboiler see Barnwell and Morris (1982) and Meili (1990). Heat pumps are also used with dryers, heat being abstracted from the exhaust air and used to preheat the incoming air. The use of a heat pump with an evaporator is described in Volume 2, Chapter 14. 

The variation of refrigeration COP with heat rejection temperature (final bed adsorption temperature and condensing temperature are assumed equal) and the maximum cycle temperature is illustrated for an evaporating temperature of -5°C in Fig. 8. Heat pump COP s follow similar trends but are higher. 

For the concentration of fruit juice by evaporation, it is proposed to use a falling-film evaporator and to incorporate a heat-pump cycle with ammonia as the medium. The ammonia in vapour form enters the evaporator at 312 K and the water is evaporated from the juices at 287 K. The ammonia in the vapour—liquid mixture enters the condenser at 278 K and the vapour then passes to the compressor. It is estimated that the work required to compress the ammonia is 150 kJ/kg of ammonia and that 2.28 kg of ammonia is cycled/kg water evaporated. The following proposals are made for driving the compressor ... 

The evaporation of citrus juices at temperatures up to 328 K, or of pharmaceutical products at even lower temperatures, has led to the development of an evaporator incorporating a heat-pump cycle using a separate working fluid. The use of the heat pump cycle, with ammonia as the working fluid is shown in Figure 14.13. In this arrangement, ammonia... 

An example of a heat pump is a house heat pump, which is made up of a compressor, a condenser, a throttling valve, and an evaporator. Heat (Sh) is removed to the high-temperature house from the working fluid in the condenser, work is added to the compressor by an electric motor, and heat (2l) is added to the evaporator from the low-temperature outside air in the winter season. 

The components of the basic vapor heat pump include a compressor, a condenser, an expansion valve, and an evaporator. 

Determine the COP, horsepower required, and heating load of a basic vapor heat pump cycle using R-134a as the working fluid and in which the condenser pressure is 900 kPa and the evaporation pressure is 240 kPa. The circulation rate of fluid is O.lkg/sec. Show the cycle on a T-s diagram. Plot the sensitivity diagram of COP versus condenser pressure. 

Find the compressor power required, quality of the refrigerant at the end of the throttling process, heating load, and COP for a heat pump that uses R-12 as the working fluid and is designed to operate at an evaporator saturation temperature of 10°C and a... 

An ideal heat pump uses ammonia as the working fluid. The saturation temperature of the refrigerant in the evaporator is 22°F and in the condenser it is 98°F. The refrigerant is circulated at the rate of 0.051 Ibm/sec. Determine the compressor power required, heating load, and COP of the heat pump. 

---