Heat Transfer in a Heat Exchanger

This Demonstration calculates and plots the heat flow, (in watts/), through a heat exchanger's wall of a chosen thickness, (in mm), and thermal conductivity, (in watts/m °C), with chosen surface heat transfer coefficients at either side of the wall, and (in watts/ °C), and logarithmic mean temperature difference, Δ (in °C), between them. Since the heat transfer coefficients can vary over a very large range, the and parameters can be specified as being high or low using a setter bar. The calculations are done using the equation , whose parameters can be modified by moving sliders. The red dot on the plot marks the heat flow per unit area for a Δ chosen by moving the top slider. The top graphic depicts the heat resistances as a schematic diagram (not to scale).

SNAPSHOTS

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DETAILS

Snapshot 1: heat transfer through a thin, good conducting wall with flowing liquid on the inside and moving air on the outside
Snapshot 2: heat transfer through a thick, good conducting wall with flowing liquids on both sides
Snapshot 3: heat transfer through a thick, poorly conducting wall with flowing liquids on both sides
Snapshot 4: heat transfer through a thick, poorly conducting wall with condensing liquids on both sides
Reference: R. L. Earle with M. D. Earle, Unit Operations in Food Processing, NZIFST, Inc., 1983. (http://www.nzifst.org.nz/unitoperations/)
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