Impact of Fe powder sintering and soldering in production of porous heating surface on flow boiling heat transfer in minichannels

Abstract

Abstract. This paper focuses on identification of the impact of porous heated surface on flow boiling heat transfer in a rectangular minichannel. The heated element for Fluorinert FC-72 was a thin plate made of Haynes-230. Infrared thermography was used to determine changes in the temperature on its outer smooth side. The porous surface in contact with the fluid in the minichannel was produced in two processes: sintering or soldering of Fe powder to the plate. The results were presented as relationships between the heat transfer coefficient and the distance from the minichannel inlet and as boiling curves. Results obtained for using a smooth heated plate at the saturated boiling region were also presented to compare. In the subcooled boiling region, at a higher heat flux, the heat transfer coefficient was slightly higher for the surface prepared via soldering. In the saturated boiling region, the local heat transfer coefficients obtained for the smooth plate surface were slightly higher than those achieved from the sintered plate surface. The porous structures formed have low thermal conductivity. This may induce noticeable thermal resistance at the diffusion bridges of the sintered structures, in particular within the saturated boiling region.

Enhanced Surfaces Used in Research on Flow Boiling Heat Transfer in Minichannels

“…As a result, the cathode surface is covered with pure anode material or a layer created by the mutual impacts between electrodes and the medium between electrodes. The intensity of the transfer of the material depends mainly on impulse energy [2,9]. Sample cavities in the 0.10 mm thick Haynes-230 alloy surface section were made by electromachining, using an electric-etcher and branding-pen manually controlled and oriented in selected directions.…”

“…One of the methods of heat transfer enhancement involves heat transfer surface modification. The modification causes the increase of heat transfer coefficient values through increasing the number of active nucleation sites during flow boiling [1][2][3][4][5][6][7][8][9][10] or pool boiling [10][11][12]. Modified surfaces exhibit reduced surface superheating and improve heat dissipation by increasing the area of heat removal.…”

“…In their previous articles, the authors of this paper reported their findings concerning various enhanced heat transfer surfaces with the flow of various working fluids through rectangular heat exchangers with minichannels. The surfaces studied included laser-textured surfaces with regular recesses [2,7], vibration-assisted laser-textured surfaces [3,4,6], surfaces with irregular recesses obtained in the process of spark erosion [1,2,5,6,10,11], surface with capillary-fibrous structure [1] and powder surfaces produced by sintering or soldering [8,9]. Based on the research results for flow boiling in minichannels, this article discusses the enhanced surfaces used, along with their production methods and effects on heat transfer processes.…”

Characteristics of Refrigerant Boiling Heat Transfer in Rectangular Mini-Channels during Various Flow Orientations

“…At Kielce University of Technology, previous investigations on boiling heat transfer during cooling liquids' flow [19][20][21] along rectangular mini-channels of changeable spatial orientation, with smooth or modified heater surfaces, were discussed in [20,22,23]. The thermoelasticity problem was the main topic of References [24,25] dealing with a two-layer plate [24] and non-contacting face seals [25].…”

“…Higher HTC for higher q w , for the surface produced by soldering iron powder [23] Figure 15a-d Boiling curves are essential to recognize heat transfer mechanisms in flow boiling. The boiling curves shown in Figure 16 were generated on the basis of the experimental data during increasing heat flux supplied to the mini-channel's heated plate.…”