Convective Heat Transfer by Impingement of Circular Liquid Jets

Abstract

The impingement of circular, liquid jets provides a convenient method of cooling surfaces. Here, jet impingement cooling of uniformly heated surfaces is investigated analytically and experimentally for stable, unsubmerged, uniform velocity laminar jets in the absence of phase change. Analytical and numerical predictions are developed for a laminar radial film flow. Experiments using undisturbed laminar jets were performed to determine local Nusselt numbers from the stagnation point to radii of up to 40 diameters. Turbulent transition in the film flow is observed experimentally at a certain radius. Beyond this transition radius, a separate turbulent analysis is constructed. Integral method results are compared to numerical results, and Prandtl number effects are investigated. The predictions are found to agree well with the measurements for both laminar and turbulent flow. Predictive formulae are recommended for the entire range of radii.

Experimental and Numerical Studies of Evaporation Local Heat Transfer in Free Jet

“…Figure 7 also indicates that in the parallel flow, radial velocity is not uniform and it is lower than inlet jet velocity at the nozzle exit. The present results contradicts the assumption of some authors (Liu et al 1989, Liu et al 1991 assuming that the flow is fully developed before the hydraulic jump, and the free surface velocity is equal to the exit average jet velocity. Experimental results are compared with the laminar and the turbulent theories predictions defined by Watson (1964) in figures 8a and b.…”

“…Location of hydraulic jump on the surface is an interest physical phenomenon. In the previous work, some authors (Stevens & Webb, 1992, 1993, Liu et al 1991, Watson, 1964 show the influence of the jet mass flow rate on the hydraulic jump radius that is defined at the radius location where the liquid layer depth attains a highest value in the parallel flow (Figure 6a). For Reynolds number ranging from 700 to 5000, Figure 6b shows dimensionless hydraulic jump radius as a function of Reynolds number.…”

Heat Transfer Characteristics of a Pipe-laminar Jet Impinging on a Moving Hot Solid

“…Wang et al, 8) Liu et al, 9) and Zhao and Ma 10) proposed the following equations: where q, λ f , v f , T w and T f denote the heat flux, thermal conductivity of water, kinematic viscosity coefficient of water, local temperature of the wet surface, and temperature of water, respectively. D j and V j were calculated using a simple mass conservation law as…”

“…Furthermore, theoretical and empirical correlations capable of predicting heat transfer characteristics in steady state have been proposed [8][9][10][11] under conditions that the temperature of the solid is below the boiling temperature of the liquid and the heat flux from the solid to the liquid is constant. In order to validate the present experimental procedure and data reduction method, experiments were conducted in this study under such conditions and the obtained data were compared with the correlations.…”

Experimental study on the method and performance for heat transfer of jet impingement

“…Therefore, a lot of researches about the influences from structure of jet and working fluid for heat transfer have been made, especially when the water is regarded as the working fluid. The heat transfer characteristics of water under the circumstances of low temperature below 40 have been ℃ given out by Liu [1] through carrying out a large number of experimental studies, and a classical correlation at stagnation point has been given out. Ma & Zhao [2] also have given out a heat transfer correlation at the stagnation by combining the theoretical calculation with experimental method with seven coolants under the condition of lower temperature.…”