Ma. Abdelghani-idrissi et al., Analytical and experimental response time to flow rate step along a counter flow double pipe heat exchanger, INT J HEAT, 44(19), 2001, pp. 3721-3730
Temperatures transient response along a tubular counter flow heat exchanger
is investigated when mass flow rate is subjected to sudden change. The dyn
amic behaviour is approximated by a first order response with a time consta
nt. The hot fluid subjected to the flow rate step presents a decreasing lin
ear time constant according to flow axis. The cold fluid, which is not subm
itted to the flow rate step, shows two types of transient response. The fir
st one corresponds to a linear spatial increasing function of time constant
while the second one presents a uniform time constant along the heat excha
nger. Considering the conditions of the transient response on the boundarie
s of the heat exchanger, analytical expressions of time constants are obtai
ned for each case, The comparison of the theoretical results with experimen
tal data allows to validate the analytical expressions, which depend on ini
tial and final steady-states. The influence of the flow rate step magnitude
on transient behaviour is studied by maintaining the initial steady-state.
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