Effect of geometrical design on the latent heat cooling properties of a lightweight two-phase composite

2021 ◽  
Vol 119 (14) ◽  
pp. 141908
Author(s):  
Ian P. Seetoh ◽  
Daniel Jovin ◽  
Chang Quan Lai
Keyword(s):  
Latent Heat ◽  
Two Phase ◽  
Geometrical Design

Flow and Heat Transfer Analysis of Mist-Film Cooling on a Flat Plate

2017 ◽  
Author(s):  
Anjali Dwivedi ◽  
Ankit Verma ◽  
S. Sarkar
Keyword(s):  
Flat Plate ◽  
Latent Heat ◽  
Film Cooling ◽  
Thermal Stresses ◽  
Density Ratio ◽  
Heat Transfer Analysis ◽  
Main Stream ◽  
Two Phase ◽  
Maximum Enhancement ◽  
Cooling Effectiveness

Film cooling is one of the preferred methods for effective cooling of a gas turbine that forms a protective layer between hot flue gases and blade surface. This paper investigates the interaction of mist in the secondary flow and physics indicating the upper limit of mist concentration. Numerical simulations are performed on a flat plate having a series of discrete holes with 35 degree streamwise orientation and the holes are connected to a common delivery plenum chamber. The blowing ratio, density ratio and Reynolds number based on freestream and hole diameter (D) are 0.5, 1.2 and 15885 respectively. A two-phase mist consisting of finely dispersed water droplets of 10 micron in an airstream is introduced as the coolant from these holes. The latent heat absorbed by the evaporating droplets significantly reduces the sensible heat of the main stream, providing heat sinks that result in enhanced cooling effectiveness. The coupling between the two-phases is modelled through the interaction terms in the transport equations. Computations are performed by ANSYS Fluent 15.0 using k-ε realizable model. The results illustrate insight of complex transport phenomena associated with the mist of varying concentration from 2% to 7%. It has been observed that the maximum enhancement of cooling effectiveness reaches 43% at X/D = 10 for 2% mist by mass with an average enhancement of 26.5%. For 3% mist, the maximum enhancement becomes 80% at X/D = 16 with the average cooling enhancement of 43%. Mist concentrations 5% and beyond trend to increase average cooling because of more absorption of latent heat by droplets, but its trajectories shift towards wall, detrimental to the blade due to corrosion effect and thermal stresses.

Experimental Investigation of Fluid Motion in Pulsating Heat Pipe

2015 ◽  
Author(s):  
Hyung Yun Noh ◽  
Sung Jin Kim
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Latent Heat ◽  
High Speed ◽  
Fluid Motion ◽  
Pulsating Heat Pipe ◽  
Operating Characteristics ◽  
Two Phase ◽  
Saturation State ◽  
Circulation Mode

In this research, operating characteristics and heat transfer phenomena in 2-turn pulsating heat pipe operating in a circulation mode were experimentally investigated. Temperature, pressure and high-speed flow visualization data were obtained with the variation of diameters (1.2 mm, 1.7 mm and 2.2 mm) and input powers. The overall pressure variation from start-up to steady state was measured using the pressure transmitters in the evaporator section. Heat transfer phenomena were investigated using homogeneous-equilibrium model. Thermodynamic state of two-phase mixture at the exit of evaporator is identified as a saturation state using obtained temperature and pressure data. The ratio of sensible heat to latent heat changed with the variation of diameters and input powers. It was found that each evaporator has a different ratio and latent heat was dominant in most experimental cases.

scholarly journals Cyclone Interactions and Evolutions during the “Perfect Storms” of Late October and Early November 1991

2011 ◽  
Vol 139 (6) ◽  
pp. 1683-1707 ◽  
Author(s):  
Jason M. Cordeira ◽  
Lance F. Bosart
Keyword(s):  
Heat Release ◽  
Latent Heat ◽  
North Atlantic ◽  
Static Stability ◽  
Moist Convection ◽  
Latent Heat Release ◽  
Two Phase ◽  
The North ◽  
Warm Front ◽  
Deep Moist Convection

Abstract This paper examines the cyclogenesis of the “Perfect Storms” of late October and early November 1991 over the North Atlantic and focuses on the influence of Hurricane Grace (HG) toward their development. The two storms considered are the “Perfect Storm” (PS) that underwent a warm seclusion process and an extratropical cyclone (EC1) with two development phases. HG, which initially formed via tropical transition (TT), influenced the first phase of EC1 via reduced atmospheric static stability and enhanced low-level baroclinicity. As a result, deep moist convection and latent heat release produced maxima in midtropospheric diabatic heating and lower-tropospheric potential vorticity (PV) that aided the development of EC1. Backward air parcel trajectories and large diabatic contributions to eddy available potential energy (APE) generation suggests that EC1 developed as a diabatic Rossby vortex (DRV)-like feature. The second and explosively deepening phase of EC1 occurred as the cyclone coupled with an upper-tropospheric PV disturbance (PVD) over the eastern North Atlantic. Backward air parcel trajectories demonstrate the explosive deepening of EC1 involved airstreams originating from east of HG and from over the Labrador Sea. Parcel trajectories and a large baroclinic contribution to eddy APE generation further suggests that the two-phase development of EC1 may have involved a DRV-like feature. The subsequent recurvature and extratropical transition (ET) of HG occurred in the warm sector of the PS downstream of a second upper-tropospheric PVD over the western North Atlantic. Reduced atmospheric static stability, enhanced warm air advection, and strong latent heat release during the recurvature and ET of HG contributed to the development of a strong, zonally oriented warm front and the warm seclusion of the PS. Parcel trajectory analysis demonstrates that the PS warm seclusion involved the isolation of air parcels by a bent-back warm front that were warmed via sensible heating from the underlying Gulf Stream.

scholarly journals Latent Heat Storage in a Two-Phase Thermosyphon Solar Water Heater

2005 ◽  
Vol 128 (1) ◽  
pp. 69-76 ◽  
Author(s):  
Wen-Shing Lee ◽  
Bo-Ren Chen ◽  
Sih-Li Chen
Keyword(s):  
Energy Storage ◽  
Latent Heat ◽  
Heat Storage ◽  
Solar Water Heater ◽  
Water Heater ◽  
Two Phase ◽  
Latent Heat Storage ◽  
Solar Water ◽  
Energy Storage Material ◽  
Optimum Charge

This article experimentally studies the thermal performance of latent heat storage in a two-phase thermosyphon solar water heater, which utilizes the superior heat transfer characteristics of boiling and condensation, and eliminates drawbacks found in the conventional solar water heater. Experimental investigations are first conducted to study the thermal behavior of tricosane (paraffin wax 116), water, and sodium acetate (NaCH3COO∙3H2O) used as energy storage materials. The results indicate that tricosane provides many advantages to be the energy storage material in the latent heat storage system. This study also examines the functions of charge and discharge thermal behaviors in a two-phase thermosyphon solar water heater. The results show that the system gives optimum charge and discharge performance under 40% alcohol fill ratio and with tricosane used as the energy storage material, and displays an optimum charge efficiency of 73% and optimum discharge efficiency of 81%.

Numerical Simulation of Two Phase Change Materials Melting Process

2014 ◽  
Vol 1049-1050 ◽  
pp. 94-100
Author(s):  
Bo Bo Zhang ◽  
Yu Ming Xing ◽  
Qiang Sheng
Keyword(s):  
Numerical Simulation ◽  
Energy Storage ◽  
Temperature Distribution ◽  
Phase Change ◽  
Latent Heat ◽  
Control Function ◽  
Melting Process ◽  
Thermal Control ◽  
Heat Energy ◽  
Two Phase

Phase change thermal control technology has gained increasing focus as an emerging technology for the thermal control of spacecraft. This literature focused on melting process inside a latent heat energy storage filled with phase change material (PCM) by numerical simulation. A matrix-based enthalpy porosity theory in a three-dimensional finite volume discretization is simulated. The temperature distribution during the melting process of PCM Cerrolow-136 and CH3COONa·3H2O is obtained, based on which the thermal control function and energy storage capacity is compared. The results show that Cerrolow-136 has better performance. In different states of phase change, the temperature distribution of Cerrolow-136 is fairly uniform. Thermal control face's temperature of Cerrolow-136 is closer to phase transition temperature. In the same heat flux of 3000 W/m2, The whole process of thermal control temperature getting to 80°C for Cerrolow-136 is longer. Cerrolow-136, for its excellent characteristics, has potentially broad application in the fields of latent heat energy storage and space vehicle electronics.

Exact solution for a two-phase Stefan problem with power-type latent heat

2017 ◽  
Vol 110 (1) ◽  
pp. 1-13 ◽  
Author(s):  
Yang Zhou ◽  
Xiang-you Shi ◽  
Guo-qing Zhou
Keyword(s):  
Exact Solution ◽  
Latent Heat ◽  
Stefan Problem ◽  
Power Type ◽  
Two Phase

An Experimental Investigation on the Fluid Distribution in a Two-Phase Cooled Rack Under Steady and Transient IT Load

2019 ◽  
Author(s):  
Sadegh Khalili ◽  
Srikanth Rangarajan ◽  
Bahgat Sammakia ◽  
Vadim Gektin
Keyword(s):  
Latent Heat ◽  
High Performance ◽  
Data Centers ◽  
Cooling System ◽  
Heated Surface ◽  
Transient Behavior ◽  
Heat Fluxes ◽  
Fluid Distribution ◽  
Two Phase ◽  
Two Phase Cooling

Abstract Increasing power densities in data centers due to the rise of Artificial Intelligence (AI), high-performance computing (HPC) and machine learning compel engineers to develop new cooling strategies and designs for high-density data centers. Two-phase cooling is one of the promising technologies which exploits the latent heat of the fluid. This technology is much more effective in removing high heat fluxes than when using the sensible heat of fluid and requires lower coolant flow rates. The latent heat also implies more uniformity in the temperature of a heated surface. Despite the benefits of two-phase cooling, the phase change adds complexities to a system when multiple evaporators (exposed to different heat fluxes potentially) are connected to one coolant distribution unit (CDU). In this paper, a commercial pumped two-phase cooling system is investigated in a rack level. Seventeen 2-rack unit (RU) servers from two distinct models are retrofitted and deployed in the rack. The flow rate and pressure distribution across the rack are studied in various filling ratios. Also, investigated is the transient behavior of the cooling system due to a step change in the information technology (IT) load.

scholarly journals Multiple solutions and numerical analysis to the dynamic and stationary models coupling a delayed energy balance model involving latent heat and discontinuous albedo with a deep ocean

2014 ◽  
Vol 470 (2170) ◽  
pp. 20140376 ◽  
Author(s):  
J. I. Díaz ◽  
A. Hidalgo ◽  
L. Tello
Keyword(s):  
Energy Balance ◽  
Latent Heat ◽  
Deep Ocean ◽  
Initial Boundary ◽  
Initial Boundary Value Problem ◽  
Ocean Model ◽  
Energy Balance Model ◽  
Balance Model ◽  
Finite Volume Scheme ◽  
Two Phase

We study a climatologically important interaction of two of the main components of the geophysical system by adding an energy balance model for the averaged atmospheric temperature as dynamic boundary condition to a diagnostic ocean model having an additional spatial dimension. In this work, we give deeper insight than previous papers in the literature, mainly with respect to the 1990 pioneering model by Watts and Morantine. We are taking into consideration the latent heat for the two phase ocean as well as a possible delayed term. Non-uniqueness for the initial boundary value problem, uniqueness under a non-degeneracy condition and the existence of multiple stationary solutions are proved here. These multiplicity results suggest that an S-shaped bifurcation diagram should be expected to occur in this class of models generalizing previous energy balance models. The numerical method applied to the model is based on a finite volume scheme with nonlinear weighted essentially non-oscillatory reconstruction and Runge–Kutta total variation diminishing for time integration.

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