Thermal Management of Outdoor Electronic Cabinets Using Soil Heat Exchangers

2002 ◽  
Vol 124 (1) ◽  
pp. 7-11 ◽  
Author(s):  
Hisham E. Hegab ◽  
Eric B. Zimmerman ◽  
Gene T. Colwell
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Heat Dissipation ◽  
Element Model ◽  
System Level ◽  
Telephone Companies ◽  
Innovative Methods ◽  
Temperature Trends ◽  
Transient Thermal ◽  
Power Densities

Telephone companies utilize densely packed electronics in outdoor metal cabinets for routing calls between customers. As a result of the increasing power densities of electronics, companies are looking for innovative methods of providing system level cooling such as using soil heat exchangers. Numerical simulation using a system of lumped thermal capacitances coupled to a soil finite element model is used to predict the transient thermal behavior of a cabinet. The cabinet model has been verified in previous studies by comparison with experimental measurements on a commercial telecommunications cabinet and is shown to predict temperature trends well. The effects of transient heat load, soil properties, and heat exchanger geometry are examined. Results reveal soil heat exchangers have the capability to provide the necessary cooling for relatively low power outdoor cabinets. However, the temperature of the soil surrounding the heat exchanger may increase daily if the number and spacing of pipes is not adequate to handle the desired heat dissipation load.

Transient Response of Cross Flow Heat Exchangers Subjected to Simultaneous Temperature and Flow Perturbations

2015 ◽  
Vol 799-800 ◽  
pp. 665-670
Author(s):  
Karthik Silaipillayarputhur
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Convection Heat Transfer ◽  
Cross Flow ◽  
Balance Equations ◽  
Transfer Resistance ◽  
Mass Flow Rates ◽  
Flow Heat ◽  
Transient Thermal ◽  
Central Finite Difference

This paper compares the transient thermal performance between counter and parallel cross flow heat exchangers subjected to time varying inlet mass flow rates and inlet temperatures that hasn’t been previously discussed in the available literature. Specifically the transient performance of 2 pass and 3 pass cross flow heat exchangers is discussed in this paper. In the present study the energy balance equations for the hot and cold fluids and the heat exchanger wall were solved using an implicit central finite difference method. Representative values of NTU were considered, and the NTU’s of the heat exchanger were assumed to be uniformly distributed among the heat exchanger passes. Other physically significant parameters such as the capacity rate ratio and the convection heat transfer resistance ratio were systematically varied. A detailed summary based on the observations has been presented.

Details Study of Ambient Wind Effect on Heat Dissipation Capacity of Thermal-Powerplant Dry Cooling-Towers

2014 ◽  
Author(s):  
Masoud Darbandi ◽  
Ali Behrouzifar ◽  
Ahmad Mirhashemi ◽  
Hossein Salemkar ◽  
Gerry E. Schneider
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Heat Dissipation ◽  
Cooling Tower ◽  
Wind Effect ◽  
Circulating Water ◽  
Wind Velocities ◽  
Computational Fluid Dynamics Cfd ◽  
Dry Cooling Tower ◽  
Dry Cooling

Thermal powerplants report a reduction in their dry cooling tower performances due to surrounding wind drafts. Therefore, it is very important to consider the influence of wind velocity in cooling tower design; especially in geographical points with high wind conditions. In this regard, we use the computational fluid dynamics (CFD) tool and simulate a dry cooling tower in different wind velocities of 0, 5 and 10 m/s. To extend our calculations; we also consider the temperature variation of circulating water through the tower heat exchanger or deltas one-by-one. We show that some heat exchangers around the tower cannot reduce the circulating water temperature sufficiently. This causes an increase in the mean temperature of those heat exchangers. The worst performances can be attributed to heat exchanger located on side wind places. We will discuss the detail performance of each delta and their assembly in draft wind conditions. This study suggests some effective ways to overcome thermal-performance of cooling tower in wind conditions.

scholarly journals Leaf Vein-Inspired Bionic Design Method for Heat Exchanger Infilled with Graded Lattice Structure

Aerospace ◽  
2021 ◽  
Vol 8 (9) ◽  
pp. 237
Author(s):  
Haoyu Deng ◽  
Junpeng Zhao ◽  
Chunjie Wang
Keyword(s):  
Heat Exchanger ◽  
Heat Dissipation ◽  
Lattice Structure ◽  
Design Method ◽  
Mapping Method ◽  
Structure Design ◽  
Bionic Design ◽  
Leaf Vein ◽  
Transient Thermal ◽  
Graded Lattice

Due to its excellent performance and high design freedom, the lattice structure has shown excellent capabilities and considerable potential in aerospace and other fields. This paper proposes a method to map the biometric model to the lattice structure. Taking leaf veins as bionic objects, they are used to generate a bionic design with a gradient lattice structure to improve the performance of a heat exchanger. In order to achieve the above goals, this article also proposes a leaf vein model and a mapping method that combine the leaf vein model with the lattice structure. A series of transient thermal finite element simulations was conducted to evaluate and compare the heat dissipation performance of different designs. The analysis results show that the combination of the bionic design and the lattice structure effectively improves the heat dissipation performance of the lattice structure heat exchanger. The results indicate that the application of bionic design in lattice structure design has feasibility and predictable potential.

Multiscale Transient Thermal, Hydraulic, and Mechanical Analysis Methodology of a Printed Circuit Heat Exchanger Using an Effective Porous Media Approach

2013 ◽  
Vol 5 (4) ◽  
Author(s):  
Eugenio Urquiza ◽  
Kenneth Lee ◽  
Per F. Peterson ◽  
Ralph Greif
Keyword(s):  
Porous Media ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Thermal Stresses ◽  
Complex Geometry ◽  
Computer Code ◽  
Mechanical Analysis ◽  
Transient Temperature ◽  
Printed Circuit ◽  
Transient Thermal

Printed circuit heat exchangers (PCHE) and the similar formed plate heat exchangers (FPHE) offer highly attractive economics due to their higher power densities when compared to more conventional shell-and-tube designs. However, their complex geometry makes them more vulnerable to damage from thermal stresses during transient thermal hydraulic conditions. Transient stresses far exceed those predicted from steady state analyses. Therefore, a transient, hydraulic, thermal, and structural analysis is needed to accurately simulate and design high performing PCHE. The overall length of the heat exchanger can be thousands of times larger than the characteristic length for the heat transfer and fluid flow. Furthermore, simulating the thermal hydraulics of the entire heat exchanger plate is very time consuming and computationally expensive. The proposed methodology mitigates this by using a multiscale analysis with local volume averaged (LVA) properties and a novel effective porous media (EPM) approach. This method is implemented in a new computer code named the compact heat exchanger explicit thermal and hydraulics (CHEETAH) code which solves the time-dependent, mass, momentum, and energy equations for the entire PCHE plate as well as hot and cold fluid streams using finite volume analysis (FVA). The potential of the method and code is illustrated with an example problem for a Heatric-type helium gas-to-liquid salt PCHE with offset strip fins (OSF). Given initial and boundary conditions, CHEETAH computes and plots transient temperature and flow data. A specially developed grid mapping code transfers temperature arrays onto adapted structural meshes generated with commercial FEA software. For the conditions studied, a multiscale stress analysis reveals mechanical vulnerabilities in the HX design. This integrated methodology using an EPM approach enables multiscale PCHE simulation. The results provide the basis for design improvements which can minimize flow losses while enhancing flow uniformity, thermal effectiveness, and mechanical strength.

Analysis of Two Fluid Four-Channel Heat Exchanger Using Finite Element Method

2015 ◽  
Vol 813-814 ◽  
pp. 658-662
Author(s):  
Kavadiki Veerabhadrappa ◽  
Dhanush Dayanand ◽  
Darshan Dayanand ◽  
Vinayakaraddy ◽  
K.N. Seetharamu ◽  
...  
Keyword(s):  
Finite Element ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Element Model ◽  
Counter Flow ◽  
Transfer Rates ◽  
Heat Exchanger Design ◽  
Dimensional Parameters ◽  
Flow Heat ◽  
Two Fluid

The development of heat exchangers from two streams to multi-stream passage arrangement becomes a key problem for heat exchanger design. In this paper, a new design is developed for multi-stream (four-channel) heat exchanger. Multi-channel heat exchangers are extensively used in refrigeration and air conditioning, chemical industries, milk pasteurization, cryogenics industries and energy-recovery applications due to their higher heat transfer rates. The focus of this study is to determine the performance of four-channel counter flow heat exchanger. The hot and cold fluids are assumed to recirculate and exchange heat between them. Finite element model of the heat exchanger is developed based on the detailed geometry and the specific working conditions with the help of which effectiveness of the four-channel heat exchanger is computed. Non-Dimensional parameters are introduced which makes the analysis more versatile. The effectiveness is computed for different values of NTU and heat capacity ratio.

Analysis of Thermal Transients for sCO2 Brayton Cycle Heat Exchangers

2019 ◽  
Author(s):  
Anton Moisseytsev ◽  
James J. Sienicki
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Thermal Loading ◽  
Power Converter ◽  
System Level ◽  
Normal Operation ◽  
Brayton Cycle ◽  
Thermal Transients ◽  
Analysis Computer ◽  
Computer Codes

Abstract The design of heat exchangers for use in a supercritical carbon dioxide (sCO2) Brayton cycle power converter must provide for acceptable performance for duty cycle events encompassing anticipated transients and postulated accidents. This paper presents the results of a comprehensive analysis of thermal transients for sCO2 cycle heat exchangers, with emphasis on the sodium-to-CO2 heat addition heat exchanger. A range of transients, from normal operation to severe accidents, were simulated with the coupled PDC and SAS4A/SASSYS-1 system level dynamic analysis computer codes. For each transient, the calculated change in the heat exchanger wall temperature is determined as a measure of the thermal loading.

scholarly journals Mathematical model of a plate fin heat exchanger operating under solid oxide fuel cell working conditions

2013 ◽  
Vol 34 (4) ◽  
pp. 3-21 ◽  
Author(s):  
Jakub Kupecki ◽  
Krzysztof Badyda
Keyword(s):  
Mathematical Model ◽  
Fuel Cells ◽  
Heat Exchanger ◽  
Power Systems ◽  
Solid Oxide Fuel Cells ◽  
Heat Exchangers ◽  
Operating Conditions ◽  
Solid Oxide ◽  
System Level ◽  
Oxide Fuel

Abstract Heat exchangers of different types find application in power systems based on solid oxide fuel cells (SOFC). Compact plate fin heat exchangers are typically found to perfectly fit systems with power output under 5 kWel. Micro-combined heat and power (micro-CHP) units with solid oxide fuel cells can exhibit high electrical and overall efficiencies, exceeding 85%, respectively. These values can be achieved only when high thermal integration of a system is assured. Selection and sizing of heat exchangers play a crucial role and should be done with caution. Moreover, performance of heat exchangers under variable operating conditions can strongly influence efficiency of the complete system. For that reason, it becomes important to develop high fidelity mathematical models allowing evaluation of heat exchangers under modified operating conditions, in high temperature regimes. Prediction of pressure and temperatures drops at the exit of cold and hot sides are important for system-level studies. Paper presents dedicated mathematical model used for evaluation of a plate fin heat exchanger, operating as a part of micro-CHP unit with solid oxide fuel cells.

scholarly journals TEG Design for Waste Heat Recovery at an Aviation Jet Engine Nozzle

2018 ◽  
Vol 8 (12) ◽  
pp. 2637 ◽  
Author(s):  
Pawel Ziolkowski ◽  
Knud Zabrocki ◽  
Eckhard Müller
Keyword(s):  
Fuel Consumption ◽  
Power Output ◽  
Waste Heat ◽  
Positive Impact ◽  
Element Model ◽  
System Level ◽  
Specific Power ◽  
Transfer Coefficients ◽  
Te Modules ◽  
Te Material

Finite element model (FEM)-based simulations are conducted for the application of a thermoelectric generator (TEG) between the hot core stream and the cool bypass flow at the nozzle of an aviation turbofan engine. This work reports the resulting requirements on the TEG design with respect to applied thermoelectric (TE) element lengths and filling factors (F) of the TE modules in order to achieve a positive effect on the specific fuel consumption. Assuming a virtual optimized TE material and varying the convective heat transfer coefficients (HTC) between the nozzle surfaces and the gas flows, this work reports the achievable power output. System-level requirement on the gravimetric power density (>100 Wkg−1) can only be met for F ≤ 21%. When extrapolating TEG coverage to the full nozzle surface, the power output reaches 1.65 kW per engine. The assessment of further potential for power generation is demonstrated by a parametric study on F, convective HTC, and materials performance. This study confirms a feasible design range for TEG installation on the aircraft nozzle with a positive impact on the fuel consumption. This application translates into a reduction of operational costs, allowing for an economically efficient TEG-installation with respect to the cost-specific power output of modern thermoelectric materials.

Analysis of the Thermal Stress at the Tubesheet in Floating-Head or U-Tube Heat Exchangers

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
Jiuyi Liu ◽  
Caifu Qian ◽  
Huifang Li
Keyword(s):  
Thermal Stress ◽  
Heat Exchanger ◽  
Temperature Difference ◽  
Heat Exchangers ◽  
Influence Factors ◽  
Area Ratio ◽  
Shell Side ◽  
Tube Heat Exchanger ◽  
Numerical Tests ◽  
Hole Area

Thermal stress is an important factor influencing the strength of a heat exchanger tubesheet. Some studies have indicated that, even in floating-head or U-tube heat exchangers, the thermal stress at the tubesheet is significant in magnitude. For exploring the value, distribution, and the influence factors of the thermal stress at the tubesheet of these kind heat exchangers, a tubesheet and triangle arranged tubes with the tube diameter of 25 mm were numerically analyzed. Specifically, the thermal stress at the tubesheet center is concentrated and analyzed with changing different parameters of the tubesheet, such as the temperature difference between tube-side and shell-side fluids, tubesheet diameter, thickness, and the tube-hole area ratio. It is found that the thermal stress of the tubesheet of floating-head or U-tube heat exchanger was comparable in magnitude with that produced by pressures, and the distribution of the thermal stress depends on the tube-hole area and the temperature inside the tubes. The thermal stress at the center of the tubesheet surface is high when tube-hole area ratio is very low. And with increasing the tube-hole area ratio, the stress first decreases rapidly and then increases linearly. A formula was numerically fitted for calculating the thermal stress at the tubesheet surface center which may be useful for the strength design of the tubesheet of floating-head or U-tube heat exchangers when considering the thermal stress. Numerical tests show that the fitted formula can meet the accuracy requirements for engineering applications.

System Level Bench Test for Trailing Arm Strength Estimation

2006 ◽  
Author(s):  
Jaychandar Muthu ◽  
Kanak Soundrapandian ◽  
Jyoti Mukherjee
Keyword(s):  
Failure Mode ◽  
Real Life ◽  
Element Model ◽  
Suspension System ◽  
System Level ◽  
Bench Test ◽  
Component Level ◽  
Arm Strength ◽  
Bench Testing ◽  
Nonlinear Finite Element Model

For suspension components, bench testing for strength is mostly accomplished at component level. However, replicating loading and boundary conditions at the component level in order to simulate the suspension system environment may be difficult. Because of this, the component's bench test failure mode may not be similar to its real life failure mode in vehicle environment. A suspension system level bench test eliminates most of the discrepancies between simulated component level and real life vehicle level environments resulting in higher quality bench tests yielding realistic test results. Here, a suspension level bench test to estimate the strength of its trailing arm link is presented. A suspension system level nonlinear finite element model was built and analyzed using ABAQUS software. The strength loading was applied at the wheel end. The analysis results along with the hardware test correlations are presented. The reasons why a system level test is superior to a component level one are also highlighted.

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