The measurement and analysis of frost accummunlation on a flat plate with forced convection
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Frost fouling of heat exchanger surfaces is a common problem in many industrial, commercial and domestic applications. In this study the frost formation process on a flat plate with forced convection was experimentally investigated. A flat plate heat exchanger test loop was designed, built and tested. Air from the room passed over the cold test plate. Test conditions were limited to a test surface temperature range from -15 to -5 °C, air humidity ratio range from 0.004 to 0.01 kg/kg, supply air temperature range from 15 to 23 °C, and inlet airflow Reynolds number range from 3000 to 7000 (ie. air velocity from 1.15 to 2.67 m/s). An innovative new method, using a laser-beam and light-meter for the measurement of frost thickness, was designed and calibrated with an accuracy of 0.025 mm. Also, a newly designed method of measuring the local frost mass concentration (mass per unit area) was developed and tested. A calibrated heat-flux meter was used to measure the local heat flux along the test plate. Typical frost thickness, mass concentration and heat flux data are presented as a function of distance from the leading edge, humidity ratio of the inlet air, test surface temperature, inlet velocity (or Reynolds number), and time. Frost property data from more than 50 test runs are correlated against the five independent test variables using dimensionless variables. The coefficients of tolerance range from 0.91 to 0.96 for the independent variables over the range of test conditions. These data and correlations are discussed and compared with other available data in the literature.