Author: Andrea C. AshwoodPublisher:
ISBN:
Category :
Languages : en
Pages : 144
Book Description
Fluid Property Effects on Spray Cooling
Author: Andrea C. AshwoodHeat Transfer and Film Thickness Characteristics of Spray Cooling with Phase Change
Author: Adam G. PautschEffect of Surface Material Properties and Surface Characteristics in Evaporative Spray Cooling
Author: M. S. SehmbeyCharacterization and Numerical Modeling of Momentum Driven Spray Cooling
Author: Curtis LaneSpray Impingement Cooling
Author: Ri LiPublisher:
ISBN:
Category : Electronic books
Languages : en
Pages : 0
Book Description
The cooling of a surface can be achieved by the impingement of spray, which is a free surface flow of droplets ejected from a spray nozzle. Spray cooling can provide uniform cooling and handle high heat fluxes in both single phase and two phases. In this chapter, spray cooling is reviewed from two aspects: the entire spray (spray level) and droplets (droplet level). The discussion on the spray level is focused on the spray cooling performance as a function of fluid properties, flow conditions, surface conditions, and nozzle positioning. The advantages and barriers of using spray cooling for engineering applications are summarized. The discussion on the droplet level is focused on the impact of droplet flow on film flow, which is the key flow mechanism in spray cooling. Droplet flow involves single droplet, droplet train (continuously droplets broke up from jet flow), and droplet burst (droplet groups affecting at a constant frequency), and local cooling enhancement due to droplet flow is discussed in details. Future work and unresolved issues in spray cooling are proposed.
Effect of Spray Characteristics on Spray Cooling with Liquid Nitrogen
Author: Maninder S. SehmbeyExperimental Testing and Numerical Modeling of Spray Cooling Under Terrestrial Gravity Conditions
Author: Kerri Michelle BaysingerPublisher:
ISBN:
Category : Cooling
Languages : en
Pages : 116
Book Description
Baseline tests were performed for a spray cooling system using subcooled fluid under terrestrial gravity conditions, and a steady state numerical model of the glass heater pedestal assembly was built using ANSYS finite element software. A parametric study was performed to study the effects of volumetric flow rate, heat transfer rate, and orientation with respect to gravity on the experimental system. The numerical model data was compared with the experimental data in order to determine the spray heat transfer coefficient along the top of the heated surface. For a volumetric flow range gal/hr and a heat load range of W, the estimated spray heat transfer coefficient was on the order of W/(m2-K), regardless of heater orientation. In addition, the heat lost due to conduction in the upward-facing heater pedestal was estimated using both experimental and numerical results, and was found to be 1.0 greater or less than (percent of heat loss due to conduction in glass heater pedestal assembly) greater or less than 2.5%.
Spray Cooling for Land, Sea, Air and Space Based Applications, a Fluid Management System for Multiple Nozzle Spray Cooling and a Guide to High Heat Flux Heater Design
Author: Brian Scott GlassmanPublisher:
ISBN:
Category :
Languages : en
Pages : 136
Book Description
This thesis is divided into four distinct chapters all linked by the topic of spray cooling. Chapter one gives a detailed categorization of future and current spray cooling applications, and reviews the major advantages and disadvantages that spray cooling has over other high heat flux cooling techniques.
Heat Transfer Enhancement of Spray Cooling with Nanofluids
Author: Christian David MartinezPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
ABSTRACT: Spray cooling is a technique for achieving large heat fluxes at low surface temperatures by impinging a liquid in droplet form on a heated surface. Heat is removed by droplets spreading across the surface, thus removing heat by evaporation and by an increase in the convective heat transfer coefficient. The addition of nano-sized particles, like aluminum or copper, to water to create a nanofluid could further enhance the spray cooling process. Nanofluids have been shown to have better thermophysical properties when compared to water, like enhanced thermal conductivity. Although droplet size, velocity, impact angle and the roughness of the heated surface are all factors that determine the amount of heat that can be removed, the dominant driving mechanism for heat dissipation by spray cooling is difficult to determine. In the current study, experiments were conducted to compare the enhancement to heat transfer caused by using alumina nanofluids during spray cooling instead of de-ionized water for the same nozzle pressure and distance from the heated surface. The fluids were sprayed on a heated copper surface at a constant distance of 21 mm. Three mass concentrations, 0.1%, 0.5%, and 1.0%, of alumina nanofluids were compared against water at three pressures, 40psi, 45psi, and 50psi. To ensure the suspension of the aluminum oxide nanoparticles during the experiment, the pH level of the nanofluid was altered. The nanofluids showed an enhancement during the single-phase heat transfer and an increase in the critical heat flux (CHF). The spray cooling heat transfer curve shifted to the right for all concentrations investigated, indicating a delay in two-phase heat transfer. The surface roughness of the copper surface was measured before and after spray cooling as a possible cause for the delay.
Pulse Mitigation and Heat Transfer Enhancement Techniques. Volume 1. Spray Cooling
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 95
Book Description
This report presents an experimental and theoretical investigation of spray cooling. A complete study is presented for surfaces maintained between the fluid saturation temperature and the Leidenfrost temperature. Experiments were conducted to analyze the effects of spray and surface conditions on the heat transfer. Different mechanisms causing the critical heat flux (CHF) are identified. For dropwise evaporation, CHF results when the surface heat flux exceeds the latent heat content of the spray. As the flow rate is increased, droplet conglomeration and surface flooding result. For low flow rate cases with a flooded surface, CHF is caused by a liquid deficiency resulting from droplet expulsion caused by the nucleating bubbles within the liquid film. For higher flow rate cases, CHF occurs when the vapor generation rate on the surface is so high that a vapor barrier is formed.