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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 ...
Assume heat transfer [2] is occurring in a heat exchanger along an axis z, from generic coordinate A to B, between two fluids, identified as 1 and 2, whose temperatures along z are T 1 (z) and T 2 (z). The local exchanged heat flux at z is proportional to the temperature difference:
Temperature vs. heat load diagram of hot stream (H 2 O entering at 20 bar, 473.15 K, and 4 kg/s) and cold stream (R-11 entering at 18 bar, 303.15 K, and 5 kg/s) in a counter-flow heat exchanger. "Pinch" is the point of closest approach between the hot and cold streams in the T vs. H diagram.
The overall heat transfer coefficient is a measure of the overall ability of a series of conductive and convective barriers to transfer heat. It is commonly applied to the calculation of heat transfer in heat exchangers, but can be applied equally well to other problems.
Tubular heat exchanger Partial view into inlet plenum of shell and tube heat exchanger of a refrigerant based chiller for providing air-conditioning to a building. A heat exchanger is a system used to transfer heat between a source and a working fluid. Heat exchangers are used in both cooling and heating processes. [1]
Concentric Tube (or Pipe) Heat Exchangers are used in a variety of industries for purposes such as material processing, food preparation, and air-conditioning. [1] They create a temperature driving force by passing fluid streams of different temperatures parallel to each other, separated by a physical boundary in the form of a pipe.
A shell-and-tube heat exchanger is a class of heat exchanger designs. [1] [2] It is the most common type of heat exchanger in oil refineries and other large chemical processes, and is suited for higher-pressure applications. As its name implies, this type of heat exchanger consists of a shell (a large pressure vessel) with a bundle of tubes ...
[4] [5] In recent years Wang [6] [7] unified all the main existing models and developed a most completed theory and design tool. The total rate of heat transfer between the hot and cold fluids passing through a plate heat exchanger may be expressed as: Q = UA∆Tm where U is the Overall heat transfer coefficient, A is the total plate area, and ...