Heat Transfer Calculations during Flow in Mini-Channels with Estimation of Temperature Uncertainty Measurements

Abstract

The main aim of this work was to provide heat transfer calculations of flow boiling in mini-channels with an application for the Trefftz functions. The test section comprised five parallel mini-channels with a depth of 1 mm, with a common heated wall. For the estimation of the temperature uncertainty, during the experiment the temperature measurement was performed with the use of K-type thermoelements and an infrared camera in two mini-channels simultaneously. According to the Guide to the Expression of Uncertainty in Measurement, the Monte Carlo method is a practical alternative to the GUM uncertainty framework. Since the uncertainty components are not approximately the same magnitude, the Monte Carlo method was indicated to estimate the uncertainty of the surface temperature measurement. The results obtained from this simulation method were compared with the results of the computation related to the uncertainty propagation method. The results of both methods of temperature measurement were found to be consistent. The results of the statistical analysis were used to describe heat transfer calculations. The heat transfer investigations concerning the subcooled boiling region were performed during the other experiment. The local heat transfer coefficients on the contact surface between the working fluid and the heated wall were calculated from the Robin boundary condition. The mathematical model described by the heat equation in the mini-channel wall and by the Fourier-Kirchhoff equation in a flowing fluid leads to an inverse heat transfer problem. This problem was solved using the FEM with the Trefftz-type basis functions. The estimation of temperature uncertainty measurements due to the Monte Carlo method was included in the final results of the heat transfer coefficient.

Using Quality Function Deployment to Assess the Efficiency of Mini-Channel Heat Exchangers

“…Because the technical features of the compact heat exchanger are strictly defined by the specific intended use, the priority of these parameters is the highest at the design stage. The HOQ fields (3) were assumed on the basis of the experimental results collected in the experimental research [26,29,30,35].…”

“…∆q-the accuracy of the calculated heat flux density was estimated in parallel to [28], considering errors of: current intensity (supplied to the heated plate), voltage drop (across the heated plate), and area of the heated plate; ∆T h = ∆T + ∂T h ∂x ∆x -the accuracy of the heated plate temperature; ∆T f ,ave = ∆T f + ∂T f ,ave ∂x ∆x -the accuracy of the fluid temperature; with the following assumptions: ∆T = 2 K-uncertainty of the heated plate temperature, measured by the FLIR A655SC infrared camera (FLIR Systems Inc., Wilsonville, OR, USA), while the accuracy of this camera is ±2 • C or ±2% in the temperature range of −20 ÷ 120 • C (see Table 5); ∆T f = 0.34 K-uncertainty of fluid temperature data obtained with additionally calibrated K-type thermocouples, analogous to [30]; ∆x = 0.0001 m-uncertainty of infrared thermography temperature measurement location, as in [35].…”

Investigations of Flow Boiling in Mini-Channels: Heat Transfer Calculations with Temperature Uncertainty Analyses

“…Estimation of the uncertainty of the temperature measurement by the thermocouples was also carried out by using the Monte Carlo (MC) method. The calculations were performed in the Mathematica program of Wolfram Research, ver 13, according to the recommendations formulated in the guide [13] using the algorithm described in the article [35].…”

An Experimental Investigation and Numerical Simulation of Photovoltaic Cells with Enhanced Surfaces Using the Simcenter STAR-CCM+ Software

“…The camera is characterised by a temperature measurement accuracy of ±2 • C or ±2% a measured temperature range according to its manufacturer [16]. Furthermore, the proposed method for the estimation of temperature uncertainty measurements based on the Monte Carlo method was described in detail in [17]. In this method, experimental data were collected with the use of a FLIR A655SC infrared camera.…”