Abstract
The paper discusses the results of the flow boiling heat transfer in a vertical minichannel with rectangular cross-section. The heating element for FC-72 flowing in the minichannel is a thin plate. Infrared thermography is used to determine changes in the temperature on its outer side. The aim of thecalculation is to determine the heat transfer coefficient using 1D and 2D calculation models. Local values of heat transfer coefficient on the surface between the heated plate and boiling fluid are calculated from the Newton`s and Fourier`s laws. In 2D model the plate temperature distribution is obtained by solving the inverse heat conduction problem. The governing equation is solved by means of two methods: the non-continuous Trefftz method and the Beck method. The results are presented as plate temperature and heat transfer coefficient calculated using 1D and 2D models as a function of the distance fromthe minichannel inlet. The analysis of the results revealed that the values and distributions of the heat transfer coefficient calculated by means of both models were similar. This suggests that all mentioned methods are interchangeable.
Highlights
The mechanism of heat transfer in minichannels is a complicated phenomenon not fully understood yet
The local values of the heat transfer coefficient obtained from 1D model were higher in comparison to determined according to 2D model with using the Beck and the non-continuous Trefftz methods at three values of inlet pressure (Fig. 5) and three values of heat flux (Fig. 6)
The analysis of the results revealed that the values and distributions of the heat transfer coefficient calculated by means of 1D model and 2D model using the Beck and the non-continuous Trefftz methods, were similar at the same heat flux supplied to the heated plate
Summary
The mechanism of heat transfer in minichannels is a complicated phenomenon not fully understood yet. In the literature, [7,8,9,10] the results of pool boiling heat transfer when the enhancement of the heated surface was applied in the form of mini-fins were described. The heat transfer coefficient in flow and pool boiling was calculated by using analytical method in articles [16,17,18]. The two-dimensional calculation model was presented by the authors e.g. in [21, 22] This model was proposed to identify the heat transfer coefficient at the flowing fluid-heated wall contact surface the wall temperature, the fluid temperature and the wall temperature gradient, by solving the inverse heat transfer problem [23]. For the inverse heat transfer problem solving other methods as Hybrid Picard-Trefftz Method [32] and Fourier transform can be applied [33]
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