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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).
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.
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]
The fins also serve to increase the structural integrity of the heat exchanger and allow it to withstand high pressures while providing an extended surface area for heat transfer. A high degree of flexibility is present in plate-fin heat exchanger design as they can operate with any combination of gas, liquid, and two-phase fluids. [3]
[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 ...
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 ...
Pillow-plate heat exchangers are a class of fully welded heat exchanger design, which exhibit a wavy, “pillow-shaped” surface formed by an inflation process. Compared to more conventional equipment, such as shell and tube and plate and frame heat exchangers, pillow plates are a quite young technology. Due to their geometric flexibility ...
Examples are the Waukesha Cherry-Burrell Votator II, Alfa Laval Contherm, Terlet Terlotherm and Kelstream's scraped surface heat exchanger. Another example is the HRS Heat Exchangers R Series or Sakura Seisakusho Ltd. Japan Onlator. Reciprocating, tubular DSSHEs. The shaft is concentric to the tube and moves longitudinally without rotating.