Heat pumps basics

Carnot Refrigerator and Heat Pump Basic Vapor Refrigeration Cycle Actual Vapor Refrigeration Cycle Basic Vapor Heat Pump Cycle Actual Vapor Heat Pump Cycle Working Fluids for Vapor Refrigeration and Heat Pump Systems Cascade and Multistaged Vapor Refrigerators... 

Cryogenic distillation has been used extensively ia the processiag of natural gas for nitrogen removal and for helium recovery (22—23). Two basic processes are now used for nitrogen rejection from natural gas— the single-column heat-pumped process and the double-column process. Eadier processes utilized multistage flash columns for helium recovery from natural gas (24). 

Figs. 9 and 10 below show the COP s of refrigerators and heat pumps respectively in the basic cycle deseribed in Seetion 2... 

The applieation of aetivated earbons in adsorption heat pumps and refrigerators is diseussed in Chapter 10. Sueh arrangements offer the potential for inereased efficiency because they utilize a primary fuel source for heat, rather than use electrieity, which must first be generated and transmitted to a device to provide mechanical energy. The basic adsorption cycle is analyzed and reviewed, and the ehoiee of refrigerant-adsorbent pairs discussed. Potential improvements in eost effeetiveness are detailed, including the use of improved adsorbent carbons, advanced cycles, and improved heat transfer in the granular adsorbent earbon beds. 

The annual cycle energy system (ACES) has two basic components a very large insulated storage tank of water and a heating-only heat pump. The tank contains coils of pipe filled with brine (salt water) warmed by the water in the tank. The brine circulates through a heat exchanger and transfers its heat to the heat pump refrigerant. 

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

The T-s diagram of the basic vapor heat pump cycle, which consists of the following four processes, is shown in Fig. 6.10 ... 

Applying the first and second laws of thermodynamics of the open system to each of the four processes of the basic vapor heat pump yields ... 

Figure 6.10 Basic vapor heat pump T-S diagram.

The desirable energy output of the basic vapor heat pump is the heat removed from the condenser (or heat added to the high-temperature thermal reservoir). The energy input to the cycle is the compressor work required. Thus, the COP of the cycle is... 

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. 

Figure 6.11a Basic vapor heat pump cycle.

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... 

There are two basic cycles for heat pump operation conventional (15) and temperature upgrading (3, J/[). It is convenient to visualize the operation of these cycles by following the changes in pressure and temperature of each alloy on a Van t Hoff plot. For ease of narration, these curves are idealized. Many engineering properties of metal hydrides must be considered in a detailed explanation (e.g., hysteresis, plateau slope, cyclic stability, etc.). The two cycles are shown in Figure 17. 

The basic equation for reversible heat pumping is, of course... 

A basic difference between distillation operations is in the handling of the heat removed by the condenser at the top of the column. The more common approach is to waste that heat by rejecting it into the cooling water. Figure 2.81 illustrates this configuration and identifies its main components. An alternate configuration (not shown) is to recycle the heat instead of wasting it. This is done by a heat pump (compressor), which moves the heat from the condenser into the reboiler. 

The developed mathematical model has been applied for calculation of processes in MHHP intended for vehicle air conditioning [4, 7]. Study of influence of the basic heat pump parameters (pressure of hydrogen charging, temperatures and coolant consumption, cycle time) on its power characteristics has been carried out. It was shown that the estimated data well agreed with experimental results. It was found that the developed model could be used for qualitative investigation of various parameters influence and approximate quantitative assessments. 

For the developed mathematical model of HHP alternative calculations have been carried out with the purpose of search of optimum values of regime parameters for concrete installations [7, 8], It has been determined, that there are optimum initial pressure in sorbers of HHP, optimum temperature modes (at levels of temperatures Th, Tm, T ), providing the maximal efficiency. Optimization of control by HHP operation it is possible to achieve optimum characteristics of capacity and to choose necessary duration of a cycle of HHP. Control of the hydride heat pump is its essential part and as show the carried out calculations [7, 8], essentially influences efficiency of its operation. Experimental results basically have proved mathematical calculations. 

A heat pump system utilizes a heat exchanger buried in water-saturated soil as a heat source. The heat exchanger basically consists of a series of vertical plates with height of 30 cm and a width of 10 cm. These plates are effective Is at a uniform temperature of 5°C. The soil can be assumed to have a permeability of 10 0 nr and apparent thermal conductivity of 0.1 W/m-K. The temperature of the saturated soil far from the heat exchanger is 30°C. Assuming natural convective flow and that there is no interference between the flows over the individual plates, find the mean heat transfer rate to a plate. 

The basic components of the heat pump system comprise an expansion valve, two heat exchangers (evaporator and condenser), and a compressor. A schematic diagram depicting the operation of a heat pump dryer is shown in Figure 55.2. 

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