Two-Phase Fin-Induced Turbulent Cooling for Electronic Devices Using Heat Pump Associated Micro-Gap Heat Sink

2018 ◽  
Vol 7 (3.13) ◽  
pp. 113
Author(s):  
Shugata Ahmed ◽  
Erwin Sulaeman ◽  
Ahmad Faris Ismail ◽  
Muhammad Hasibul Hasan
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flow Field ◽  
Heat Transfer Rate ◽  
Heat Pump ◽  
Transfer Rate ◽  
Electronic Devices ◽  
Numerical Results ◽  
Two Phase ◽  
Heater Temperature

High energy requirement for electronic cooling is a major problem to operate high performance computers and data centres. Developing low cost thermal management systems for micro-electronic devices and micro-electro-mechanical systems (MEMS) is a cutting edge research area. A heat pump system associating micro-gap evaporator with internal micro-fins is a potential candidate for two-phase cooling of these advanced devices. Micro-fins induce pseudo-turbulence in the flow field, which escalates heat transfer rate. In this paper, the system performance of a heat pump using micro-gap evaporator has been investigated numerically and experimentally. As heat transfer rate in the micro-gap evaporator is influenced by turbulence generation, flow field in the inlet and outlet manifolds have been visualized in the numerical simulation to observe fin-induced pseudo-turbulence at the entrance and outlet of the micro-gap evaporator. The simulation has been performed using FLUENT 14.5 release. Experimental work has been carried out to validate numerical results. For experimentation purpose, a test rig has been developed, which contains a test section accommodating the micro-gap evaporator. A heater is provided at the bottom of the evaporator to supply uniform heat flux ranging 1 ~ 8 kW/m2. A pre-heater is installed at the compressor outlet to vary refrigerant temperature at the condenser inlet. The range of pre-heater temperature is 93 ~ 159°C. A variable speed compressor is used. The input frequency to the compressor is varied within the range of  20 ~ 50 Hz to run the compressor at different speeds. Experimental data show good agreement with numerical results. It is observed that in transient state, temperatures and pressures at different locations of the test apparatus fluctuate due to quasi-periodic dry out and surface rewetting nature of the flow. When pre-heater temperature is set at 159⁰C and compressor frequency is increased from 20 Hz to 30 Hz, evaporator wall heat flux escalates 118.2% and heat transfer rate of the condenser increases 65.2%. However, heat transfer rate declines with the further increment of compressor frequency. Coefficient of performance (COP) of the heat pump also increases with the frequency increment from 20 Hz to 30 Hz and declines after surpassing 40 Hz frequency. 

scholarly journals Control temperature fluctuations in two-phase CuO-water nanofluid by transfiguration of the enclosures

2020 ◽  
pp. 334-334
Author(s):  
Hadi Pourziaei Araban ◽  
Javad Alinejad ◽  
Ganji Domiri
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Natural Convection ◽  
Heat Transfer Rate ◽  
Wall Temperature ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Temperature Fields ◽  
Two Phase ◽  
Flux Boundary Condition

The innovation of this paper is to simulate two-phase nanofluid natural convection inside the transformable enclosure to control the heat transfer rate under different heat flux. Heat transfer of a two-phase CuO-water nanofluid in an enclosure under different heat flux has many industrial applications including energy storage systems, thermal control of electronic devices and cooling of radioactive waste containers. The Lattice Boltzmann Method based on the D2Q9 method has been utilized for modeling velocity and temperature fields. Streamlines, isotherms and nanoparticle volume fraction, have been investigated for control the heat transfer rate for several cases. The purpose of this feasibility study is to achieve uniform temperature profiles and Tmax < 50?C under different heat flux. Natural convection heat transfer in the rectangular and parallelogram enclosures with positive and negative angular adiabatic walls were simulated. The average wall temperature under heat flux boundary condition has been studied to predict optimal levels of effective factors to control the maximum wall temperature. The results illustrated parallelogram enclosures with positive angle of case 1 and case 3 and 4 with rectangular enclosures were best cases for considering physical conditions. Average of temperature for these cases were 37.9, 29.7 and 38.2, respectively.

Numerical Research on Heat Transfer Characteristics Analysis of Two Particles in Supercritical Water

2021 ◽  
Author(s):  
Xiaoyu Li ◽  
Zhenqun Wu ◽  
Huibo Wang ◽  
Hui Jin
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Phase Flow ◽  
Heat Transfer Characteristics ◽  
Particle Cluster ◽  
Two Phase ◽  
Transfer Characteristics

Abstract In the supercritical water (SCW)-particle two-phase flow of fluidized bed, the particles that make up the particle cluster interact with each other through fluid, and it will affect the flow and heat transfer. However, due to the complex properties of SCW, the research on particle cluster is lacking, especially in terms of heat transfer. This research takes two particles as an example to study the heat transfer characteristics between SCW and another particle when one particle exists. This research uses the distance and angle between the two particles as the influencing factors to study the average heat transfer rate and local heat transfer rate. In this research, it is found that the effect is obvious when L/D = 1.1. When L = 1.1D, the temperature field and the flow field will partially overlap. The overlap of the temperature field will weaken the heat transfer between SCW and the particle. The overlap of the flow field has an enhanced effect on the heat transfer between SCW and the particle. The heat transfer between SCW and particles is simultaneously affected by these two effects, especially local heat transfer rate. In addition, this research also found that as the SCW temperature decreases, the thermal conductivity and specific heat of SCW increases, which enhances the heat transfer between SCW and the particles. This research is of great significance for studying the heat transfer characteristics of SCW-particle two-phase flow in fluidized bed.

Numerical simulation of water/alumina nanofluid mixed convection in square lid-driven cavity

2019 ◽  
Vol 30 (5) ◽  
pp. 2781-2807
Author(s):  
Davood Toghraie ◽  
Ehsan Shirani
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Mixed Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Richardson Number ◽  
Hartmann Number ◽  
Two Phase ◽  
Content Type ◽  
Driven Cavity

Purpose The purpose of this paper is to investigate the mixed convection of a two-phase water–aluminum oxide nanofluid in a cavity under a uniform magnetic field. Design/methodology/approach The upper wall of the cavity is cold and the lower wall is warm. The effects of different values of Richardson number, Hartmann number, cavitation length and solid nanoparticles concentration on the flow and temperature field and heat transfer rate were evaluated. In this paper, the heat flux was assumed to be constant of 10 (W/m2) and the Reynolds number was assumed to be constant of 300 and the Hartmann number and the volume fraction of solid nanoparticles varied from 0 to 60 and 0 to 0.06, respectively. The Richardson number was considered to be 0.1, 1 and 5. Aspect ratios were 1, 1.5 and 2. Findings Comparison of the results of this paper with the results of the numerical and experimental studies of other researchers showed a good correlation. The results were presented in the form of velocity and temperature profiles, stream and isotherm lines and Nusselt numbers. The results showed that by increasing the Hartmann number, the heat transfer rate decreases. An increase from 0 to 20 in Hartmann number results in a 20 per cent decrease in Nusselt numbers, and by increasing the Hartmann number from 20 to 40, a 16 per cent decrease is observed in Nusselt number. Accordingly, it is inferred that by increasing the Hartmann number, the reduction in the Nusselt number is decreased. As the Richardson number increased, the heat transfer rate and, consequently, the Nusselt number increased. Therefore, an increase in the Richardson number results in an increase of the Nusselt number, that is, an increase in Richardson number from 0.1 to 1 and from 1 to 5 results in 37 and 47 per cent increase in Nusselt number, respectively. Originality/value Even though there have been numerous investigations conducted on convection in cavities under various configurations and boundary conditions, relatively few studies are conducted for the case of nanofluid mixed convection in square lid-driven cavity under the effect of magnetic field using two-phase model.

scholarly journals Role of Rotating Cylinder toward Mixed Convection inside a Wavy Heated Cavity via Two-Phase Nanofluid Concept

Nanomaterials ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 1138 ◽  
Author(s):  
Ammar I. Alsabery ◽  
Mohammad Ghalambaz ◽  
Taher Armaghani ◽  
Ali Chamkha ◽  
Ishak Hashim ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Rotating Cylinder ◽  
Alumina Nanoparticles ◽  
Optimum Number ◽  
Two Phase ◽  
Rotation Direction

The mixed convection two-phase flow and heat transfer of nanofluids were addressed within a wavy wall enclosure containing a solid rotating cylinder. The annulus area between the cylinder and the enclosure was filled with water-alumina nanofluid. Buongiorno’s model was applied to assess the local distribution of nanoparticles in the host fluid. The governing equations for the mass conservation of nanofluid, nanoparticles, and energy conservation in the nanofluid and the rotating cylinder were carried out and converted to a non-dimensional pattern. The finite element technique was utilized for solving the equations numerically. The influence of the undulations, Richardson number, the volume fraction of nanoparticles, rotation direction, and the size of the rotating cylinder were examined on the streamlines, heat transfer rate, and the distribution of nanoparticles. The Brownian motion and thermophoresis forces induced a notable distribution of nanoparticles in the enclosure. The best heat transfer rate was observed for 3% volume fraction of alumina nanoparticles. The optimum number of undulations for the best heat transfer rate depends on the rotation direction of the cylinder. In the case of counterclockwise rotation of the cylinder, a single undulation leads to the best heat transfer rate for nanoparticles volume fraction about 3%. The increase of undulations number traps more nanoparticles near the wavy surface.

Prediction of Non-Uniform Frost Distribution on a Fin Tube Heat Exchanger

2013 ◽  
Author(s):  
Jieun Hwang ◽  
Keumnam Cho
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Transfer Rate ◽  
Heat Pump ◽  
Transfer Rate ◽  
Volume Flow Rate ◽  
Local Data ◽  
Tube Heat Exchanger ◽  
Side Pressure ◽  
Fin Tube

Heat exchanger experiences frost on its surface when it operates below 0°C under heating condition of the heat pump. Since frost blocks air flow through the fin tube heat exchanger, it increases air-side pressure drop and deteriorates heat transfer rate of the heat exchanger. Prediction of the frost profiles on the heat exchanger is needed to minimize the unfavorable effect on the heat exchanger by frost. The present study predicts non-uniform frost distribution on the surface of fin-tube heat exchanger and shows its accuracy by comparing with measured profiles. Fin and tube heat exchanger for heat pump was considered for the frost prediction under practical refrigerant and air conditions. Non-uniform frost pattern was predicted by using segment by segment method of the heat exchanger. Heat transfer rate and exit temperature of air and refrigerant for each segment were calculated by applying ε-NTU method. Air volume flow rate in the front of the heat exchanger was decreased as frost goes on. It was utilized for the prediction of the frost formation. Numerically predicted results were compared with measured local data. They agreed within ±10.4% under the ISO 5151 condition.

Analytical Solutions of Heat Transfer and Film Thickness in Thin-Film Evaporation

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Chunji Yan ◽  
H. B. Ma
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Heat Flux ◽  
Film Thickness ◽  
Thermal Resistance ◽  
Heat Transfer Rate ◽  
Analytical Solutions ◽  
Transfer Rate ◽  
Total Heat ◽  
Total Heat Transfer

A mathematical model predicting heat transfer and film thickness in thin-film region is developed herein. Utilizing dimensionless analysis, analytical solutions have been obtained for heat flux distribution, total heat transfer rate per unit length, location of the maximum heat flux and ratio of conduction thermal resistance to convection thermal resistance in the evaporating film region. These analytical solutions show that the maximum dimensionless heat flux is constant which is independent of the superheat. Maximum total heat transfer rate is determined for a given film region. The ratio of conduction thermal resistance to convection thermal resistance is a function of dimensionless film thickness. This work will lead to a better understanding of heat transfer and fluid flow occurring in the evaporating film region.

Instantaneous Local Heat Flux Measurements in a Small Utility Engine

2009 ◽  
Author(s):  
Terry Hendricks ◽  
Jaal Ghandhi ◽  
John Brossman
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Numerical Model ◽  
Surface Temperature ◽  
Heat Transfer Rate ◽  
Surface Heat Flux ◽  
Transfer Rate ◽  
Surface Heat ◽  
High Load ◽  
Flux Measurements

Heat flux measurements were performed in an air-cooled utility engine using a fast-response coaxial-type surface thermocouple. The surface heat flux was calculated using both analytical and numerical models. The heat flux was found to be a strong function of engine load. The peak heat flux and initial heat flux rise rate increase with engine load. The measured heat flux data were used to estimate a global heat transfer rate, and this was compared with the heat transfer rate calculated by a single-zone heat release analysis. The measured values of heat transfer were higher than the calculated values largely because of the lack of spatial averaging. The high load data showed an unexplainable negative heat flux during the expansion stroke while the gas temperature was still high. A 1D and 2D finite difference numerical model utilizing an adaptive timestep Crank-Nicholson (CN) integration routine was developed to investigate the surface temperature measurement. Applying the measured surface temperature profile to the 1D model, the resultant surface heat flux showed excellent agreement with the analytical inversion solution and captured the reversal of the energy flow back into the cylinder during the expansion stroke. The 2D numerical model was developed to observe transient lateral conduction effects within the probe and incorporated the various materials used in the construction and assembly of the heat flux sensor. The resulting average heat flux profile for the test case is shown to be slightly higher in peak and longer in duration when compared with the results from the 1D analytical inversion, and this is attributed to contributions from the high thermal diffusivity constituents in the sensor. Furthermore, the negative heat flux at high load was not eliminated suggesting that factors other than lateral conduction may be affecting the measurement accuracy.

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