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Large heat exchangers entail high investment costs. In order to reduce capital cost, in practice a minimum temperature difference (Δ T) at the pinch point is demanded, e.g., 10 °F. It is possible to estimate the heat exchanger area and capital cost, and hence the optimal Δ T minimum value.
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:
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).
Heat Transfer Across a Scraped Surface. The Canadian Journal of Chemical Engineering. pp. 213– 219. Chong, A. (2001). A Study of Scraped-Surface Heat Exchanger in Ice-Making Applications, M. Sc. Thesis. University of Toronto. "Scraped surface heat exchangers project webpage". Smith Institute. Archived from the original on 2009-03-04. Tähti ...
This equation uses the overall heat transfer coefficient of an unfouled heat exchanger and the fouling resistance to calculate the overall heat transfer coefficient of a fouled heat exchanger. The equation takes into account that the perimeter of the heat exchanger is different on the hot and cold sides.
In fracture mechanics, the energy release rate, , is the rate at which energy is transformed as a material undergoes fracture.Mathematically, the energy release rate is expressed as the decrease in total potential energy per increase in fracture surface area, [1] [2] and is thus expressed in terms of energy per unit area.
The rate of heat flow is the amount of heat that is transferred per unit of time in some material, usually measured in watts (joules per second). Heat is the flow of thermal energy driven by thermal non-equilibrium, so the term 'heat flow' is a redundancy (i.e. a pleonasm ).
Fluid flow simulation for a shell-and-tube style exchanger; The shell inlet is at the top rear and outlet in the foreground at the bottom Shell and tube heat exchanger. 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 ...