ISSN Online: 2379-1748
ISBN Flash Drive: 978-1-56700-469-4
ISBN Online: 978-1-56700-470-0
Second Thermal and Fluids Engineering Conference
TRANSIENT THERMAL CONVEXITY OF TUBULAR HEAT EXCHANGERS
Abstract
This paper deals with the transient thermal convexity of tubular heat exchangers. Recently, a fundamental
relationship based on the thermal convexity was proposed to describe the thermal behavior of heat
exchangers in steady state. This paper treats the extension of this concept to unsteady state thermal behavior
of the heat exchangers. The governing equations in transient regime of the thermal convexity coefficients are
proposed and a solution with an approximation of a first order response is suggested. The convexity
coefficients of both fluids obey to the same transient equations of the temperatures. Analytical expression of
the time constants of the thermal convexity coefficients are demonstrated along the tubular heat exchanger
when a sudden step change is applied to a mass flow rate of one of the two fluids in co-current and counter
current flow arrangements. The thermal convexity times constant of both fluids are similar to those of
temperatures compared to experimental measurements obtained from a laboratory pilot-scale heat exchanger
[17].