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Algebraic expressions for the correction factor Fhave been developed for vari- ous shell-and-tube and cross-flow heat exchanger configurations [1–3], and the results may be represented graphically. Selected results are shown in Figures 11S.1 through 11S.4 for common heat exchanger configurations.
The heat transfer analysis of a heat exchanger involves relating the total heat transfer rate to variables like inlet and outlet temperatures of the hot and cold fluids, the overall heat transfer coefficient, and the overall heat transfer surface area. The analysis is essentially based on the energy balance between the heat gained by the cold ...
Heat can be transferred by three methods. Radiation – Energy is transferred by electromag netic radiation. One example is the heating of the earth by the sun. Conduction – Energy is transferred between solids or stationary fluids by the movement of atoms or molecules. Convection – Energy is trans-ferred by mixing part of a medium with another part.
2 Φεβ 2011 · The Overall Heat Transfer Coefficient for any heat transfer equipment is obtained from , where is the heat flow per unit time (watts), A is the heated surface area and ΔT the overall temperature difference. It is usual to design equipment using practical values of U rather than from a series of film coefficients.
10 Οκτ 2017 · Once the mass flow rates and the overall heat transfer coefficient are available, the heat transfer surface area of the heat exchanger can be determined. Charts are available in many heat transfer texts from which LMTD correction factors for a variety of heat exchangers can be calculated.
Heat transfer area. dQ = U ∆T dA (3.2) where ∆T = Th − Tc. dQ = −( ̇mcp)h dTh = −Ch dTh. (3.2 − 3.3) dQ = ( ̇mcp)c dTc = Cc dTc. (3.2 − 3.3) Where Ch and Cc are the hot and the cold fluid heat capacity rates. This equation can be integrated from the lefthand side : Parallel flow :
Calculation method. The heat load of a heat exchanger can be derived from the following two formulas: 1. Heat load, Theta and LMTD calculation. = m · cp · δt (m = ; cp · δt δt = ) m · cp. = k · A · LMTD. Where: = heat load (btu/h) = mass flow rate (lb/h) cp = specific heat (btu/lb °F)
