Page 492 - Design and Operation of Heat Exchangers and their Networks

Appendix 475

Examples for two-pass crossflow heat exchangers
(MatLab code)

% Examples for two-pass crossflow heat exchangers

% For two-pass crossflow heat exchangers, Baclic (1990) summarized totally
% 72 flow arrangements and their corresponding ?-NTU relationships for
% two-pass crossflow heat exchangers classified by cross-counterflow
% or parallel-crossflow, mixed or unmixed within one or both passes,
% mixed between the passes, and unmixed between the passes with an identic
% or inverted order.
% The flow arrangement types for cross-counterflow are denoted with BAm,n
% (fluid 1 flows from pass A to pass B, and fluid 2 flows from pass B to
% pass A).
% The flow arrangement types for cross-parallelflow are denoted with ABm,n
% (fluid 1 flows from pass A to pass B, and fluid 2 flows from pass A to
% pass B). The available analytical equations for two-pass
% parallel-crossflow heat exchangers are valid only for NTUh(1) = NTUh(2).
% The subscripts m and n denote the flow patterns of fluid 1 and fluid 2,
% respectively. Let the unit for the first pass of fluid 2 be unit I, and
% the other unit (the unit for the second pass of fluid 2) be unit II.
% The values of m (for fluid 1) and n (for fluid 2) are assigned as:
%1 – mixed throughout
%2 – mixed in unit I and the interpass, unmixed in unit II
%3 – mixed in unit II and the interpass, unmixed in unit I
%4 – mixed in the interpass, unmixed in both units
%5 – unmixed throughout and entering the second pass in an inverted order
%6 – unmixed throughout and entering the second pass in an identical order
% mn = -3 for example CBA

clear

% % parameters for two-pass cross-counterflow heat exchangers
% NTUh = [0.4; 0.6];
% Rh = [2; 2];

% parameters for two-pass parallel-crossflow heat exchangers
NTUh = [0.5; 0.5];
Rh = [2; 2];