Multistage heat pump

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). 

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... 

Multistaged refrigerators and heat pumps reduce the compressor power. 

Present is enough the big global experience of construction of multistage hydride heat pumps. Here there is no opportunity in detail to analyse all features inherent in such pumps. We shall draw attention only to some integrating reasoning. 

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]. 

That efficiency of HHP could be improved at use of the multistage modes, replacing hydrides (instead of one hydride) should have lower values of a heat capacity. Also it is necessary to remember, that the most systems suggested for triple heat pumps, more reduce, than expand areas, temperatures possible for double hydride systems. Thus hydraulic and gas hydrogen systems for installations with three hydrides considerably become complicated. 

Orgaz, E., Dantzer, P. (1987) Thermodynamics of the hydride chemical heat pump III. Considerations for multistage operation, J. Less-Common Met., 131, 385-398. 

Unit operation model (black box models such as mixers, separators, component splitters, etc. models of phase separation and relaxation, heat-transfer model, multistage models, pumps and compressors, reactor models such as equilibrium reactor, stoichiometric reactor, tubular reactor, etc. see Chapter 2). 

New technologies that are likely to find acceptance over shorter time frames include combinations of well-known conventional technologies as noted earlier. Use of heat pumps, multistage operation, better control at optimum conditions, etc., will find—and indeed have already found—many applications. 

A typical fruit juice evaporation system using the heat pump cycle is shown (PI, Cl), which uses low-temperature ammonia as the heating fluid. A frozen concentrated citrus juice process is described by Charm (Cl). The process uses a multistage falling-film evaporator. A major fault of concentrated orange juice is a flat flavor due to the loss of volatile constituents during evaporation. To overcome this, a portion of the fresh pulpy juice bypasses the evaporation cycle and is blended with the evaporated concentrate. 

Microreactors provide a safe means by which reactions, including multistage schemes, can be undertaken where, otherwise, products involving unstable intermediates may be formed. This is exemplified by Fortt who showed that for a serial diazonium salt formation and chlorination reaction performed in a microreactor under hydrodynamic pumping, significant yield enhancements (15-20%) could be observed and attributed them to enhanced heat and mass transfer [77]. This demonstrates the advantage of microreactor-based synthesis where diazonium salts are sensitive to electromagnetic radiation and static electricity, which in turn can lead to rapid decomposition. Microreactors facilitate the ability to achieve continuous-flow synthesis, which is often not possible with conventional macroscale reactors and batch production. 

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