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Vapor-compression refrigeration [6] For comparison, a simple stylized diagram of a heat pump's vapor-compression refrigeration cycle: 1) condenser, 2) expansion valve, 3) evaporator, 4) compressor (Note that this diagram is flipped vertically and horizontally compared to the previous one) [7] Temperature–entropy diagram of the vapor-compression cycle.
diagram of a double-effect falling film evaporator. Condensing vapors from flash tank B1 heat evaporator A2. •1=feed •2=product •3=steam •4=vapors. In chemical engineering, a multiple-effect evaporator is an apparatus for efficiently using the heat from steam to evaporate water. [1]
A multi-evaporator system is a vapor-compression refrigeration system generally consisting of four major components: Evaporator; Compressor; Condenser; Thermal expansion valve; Sometimes in a refrigerator several loads are varied. Refrigerators used to function at different loads operated under different condition of temperatures and pressures.
In thermal engineering, the logarithmic mean temperature difference (LMTD) is used to determine the temperature driving force for heat transfer in flow systems, most notably in heat exchangers. The LMTD is a logarithmic average of the temperature difference between the hot and cold feeds at each end of the double pipe exchanger.
The Antoine equation [3] [4] is a pragmatic mathematical expression of the relation between the vapor pressure and the temperature of pure liquid or solid substances. It is obtained by curve-fitting and is adapted to the fact that vapor pressure is usually increasing and concave as a function of temperature. The basic form of the equation is:
A vapor-compression evaporator, like most evaporators, can make reasonably clean water from any water source. In a salt crystallizer, for example, a typical analysis of the resulting condensate shows a typical content of residual salt not higher than 50 ppm or, in terms of electrical conductance , not higher than 10 μS/cm .
Some systems deal with flash-gas by separating it from the refrigerant that goes to the evaporator, as that portion of the refrigerant already evaporated and will only increase superheating. [6] One key feature when preventing flash-gas is the diameter of the piping. If the pipes are too thin and long, loss of pressure and friction tend to occur.
The number of transfer units (NTU) method is used to calculate the rate of heat transfer in heat exchangers (especially parallel flow, counter current, and cross-flow exchangers) when there is insufficient information to calculate the log mean temperature difference (LMTD). Alternatively, this method is useful for determining the expected heat ...