Experimental Research on Water Boiling Heat Transfer on Horizontal Copper Rod Surface at Sub-Atmospheric Pressure

Abstract

Abstract:In recent years, water (R718) as a kind of natural refrigerant-which is environmentally-friendly, safe and cheap-has been reconsidered by scholars. The systems of using water as the refrigerant, such as water vapor compression refrigeration and heat pump systems run at sub-atmospheric pressure. So, the research on water boiling heat transfer at sub-atmospheric pressure has been an important issue. There are many research papers on the evaporation of water, but there is a lack of data on the characteristics at sub-atmospheric pressures, especially lower than 3 kPa (the saturation temperature is 24 °C). In this paper, the experimental research on water boiling heat transfer on a horizontal copper rod surface at 1.8-3.3 kPa is presented. Regression equations of the boiling heat transfer coefficient are obtained based on the experimental data, which are convenient for practical application.

Experimental Investigation on Pool Boiling Heat Transfer Performance Using Tungsten Oxide WO3 Nanomaterial-Based Water Nanofluids

“…∆T sup is the superheat temperature, which is the difference between surface and saturation temperatures. The uncertainty analysis for multiple measured variables for this experiment were calculated according to [39] as shown in Equation (5).…”

“…Thus, intensifying heat transfer performance during the boiling process is essential for saving energy and keep those systems durable. During the last decades, many efforts have been made to experimentally study the pool boiling heat transfer performance with various working fluids involving pure liquids [4,5], refrigerants [6,7], and mixtures liquids [8][9][10]. Other studies have been conducted by surface heating modifications to enhance the pool boiling heat transfer performance [11][12][13][14].…”

Boiling Pure Fluids at Sub Atmospheric Pressures

“…In this case, the heating element is tube or disc, the absolute pressure varies from 0.3 to 100 kN/m²; The heat flux covers a range of 0.1 to 446 kW/m², the heat transfer coefficient is between 0.2 and 18.6 kW/m².K; grades are stainless steel, brass and copper, the substances used are water, hydrocarbons and refrigerants, the thermo-physical parameters of fluids at saturation are draw from the NIST site ( National Institute of Standard and Technology). Figure 1 shows the relationship between the heat flux and the heat transfer coefficient for all the data points collected from the experiments [13,24], the set of plotted points follows a curve trend except for a group of points of the series [22] which deviate from the whole. The comparison of the values predicted by the correlations with the experimental data, is treated statistically by defining the error by equation 5, the mean error (6) and the correlation coefficient (7), the latter measuring the affinity between the two groups of values, the more the coefficient tends towards the unit value and the more the values calculated with the corresponding correlation approach the experimental values and give low mean errors.…”

“…The comparison of the values predicted by the correlations with the experimental data, is treated statistically by defining the error by equation 5, the mean error (6) and the correlation coefficient (7), the latter measuring the affinity between the two groups of values, the more the coefficient tends towards the unit value and the more the values calculated with the corresponding correlation approach the experimental values and give low mean errors. Kruzhlin correlation [9] Figure 2 shows the comparison of the experimental data to that calculated with the Kruzhlin correlation [9], the points are mostly near the median line, except for the series of data [22] which are increased to the experimental ones, the mean error is 48% and the correlation coefficient is 0.90.…”

“…Figure 3 indicates that the points obtained are mostly below the median line, the Mc Nelly correlation [10] underestimates the predicted values to those of the experimental values, a series of data relating to water [22] is above the set, the error mean is 40% and the correlation coefficient is 0.91. Mostinski correlation [11] Figure 4 shows a comparison of the heat transfer coefficients of the experimental data with those calculated with Mostinski's correlation [11], one set of points are concentrated above the midline another group of points is below, the average error is of the order of 73% and the correlation coefficient which indicates the affinity of the two types of values is determined and is equal to 0.90.…”