Heat pump cycles, hydride

Figure 17. Schematic hydride heat pump cycles...

Terry, L.E. "Hydrogen-Hydride Absorption Systems and Methods for Refrigeration and Heat Pump Cycles" US Patent U,055,962 Nov. 1, 1972. 

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. 

Efficiency of HHP in a refrigerator cycle as the relation of a useful cold to the spent heat Hydride heat machine, hydride heat pump... 

For influence on a temperature range (its expansion or compression) and improvements of efficiency binary heat machines (on two hydrides) have been modified for operation in multistage modes (triple heat pumps). The choice of three of hydrides and an estimation of efficiency of thermodynamic cycles for such HHP can be determined, basing on the approaches developed in [13, 14]. 

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. 

The coupling of the absorption-desorption cycles of two different hydrides (I and II) can be used to transfer heat from a low-temperature reservoir T = 7 to a high temperature reservoir T = T-. The principle of this heat pump is illustrated by fig. 53. In the first stage (a) the two metal hydrides I and II are in open communication with each other. As can be seen from the top part of fig. 53, hydride II is less stable than the hydride I. It reaches a given equilibrium pressure p at a substantially lower... 

Hot water thermostat, tank of cooling water, pumps for water pumping, gas and hydraulic main pipes and control instrumentation are parts of installation beside sorbers. Units of installation operation have cyclic character. In the first half-cycle, hydrogen is absorbed by metal hydride of a low-temperature sorber. Released heat is removed by flowing water with temperature 10-15°C. Hydrogen in a low-temperature sorber comes from a high-temperature sorber, where it is desorbed due to heating by hot water. 

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