TY - JOUR TI - PERFORMANCE IDENTIFICATION OF THE APPARATUS FOR TESTING COMPACT HEAT EXCHANGER SURFACES AU - Bačlić Branislav AU - Gvozdenac Dušan D JN - Thermal Science PY - 1997 VL - 1 IS - 1 SP - 73 EP - 92 PT - Article AB - The description of a new test apparatus designed for an on-line determination of flow friction and heat transfer characteristics of compact heat exchanger surfaces is given. The test section of the empty apparatus has been mathematically modelled for transient response. In order to increase the reliability of heat transfer data for compact heat exchanger surfaces obtainable on this apparatus, parameter identification of the empty test section model has been performed by an original statistical approach. The Statistics in each run were based on 3 x 40 temperature data acquisition during the first 12 seconds after switching on the heater and the clock. One hundred experimental runs have been performed in order to identify the following parameters: (1) time constant of the exponential inlet temperature signal, (2) maximum fluid temperature rise at various mass flow rates for constant heater power supply, (3) number of fluid-to-wall heat transfer units, (4) time constants of two thermopiles to measure the temperatures up- and downstream of the matrix. Using humid air as the working fluid, each of these parameters is correlated at a high coefficient of determination with the Reynolds number in the range 10,770 < Rea < 60,640.