Estimating Number Of Shells And Determining The Log Mean Temperature Difference Correction Factor Of Shell And Tube Heat Exchangers
Free (open access)
S. K. Bhatti, Ch. M. Krishna, Ch. Vundru, M. L. Neelapu & I. N. Niranjan Kumar
This problem aims at developing a practical and computational tool for LMTD Correction Factor ‘F’ and approximate number of shells in the process of designing a shell and tube heat exchanger. In order to analyze the performance of heat exchanger the available approaches are LMTD and effectiveness ε . Since the expressions for Log Mean Temperature Difference (LMTD) Correction Factor ‘F’ are difficult to evaluate, the traditional analysis methods rely on the heat exchanger charts. Apart from being applicable only to a particular heat exchanger, these charts are highly nonlinear and expressed in terms of the non-dimensional parameters P and R. The LMTD correction factor ‘F’ charts are particularly difficult to read in the steep regions. In this study, a simplified analytical approach for determining LMTD correction factor ‘F’ in terms of two non-dimensional parameters W and R is presented. This new approach results in a single general algebraic equation for determining the LMTD correction factor of multi-pass shell and tube heat exchangers with any number of shell passes and even number of tube passes per shell. The correction factor thus obtained is a function of number of shells N and terminal temperatures of the heat exchanger. The value of ‘F’ obtained from this new equation is in agreement with the value obtained from the graph. For a given correction factor ‘F’ and terminal temperatures of the heat exchanger, an equation for the estimation of number of shells has been derived, which is a function of correction factor ‘F’ and terminal temperatures of the heat exchanger. This eliminates all the former cumbersome iterative methods in which values are to be assumed for some factors. Keywords: LMTD correction factor, shell and tube heat exchange, multipass heat exchanger.
LMTD correction factor, shell and tube heat exchange, multipass heat exchanger.