scholarly journals Gas Cooling of a Porous Heat Source

1952 ◽  
Vol 19 (2) ◽  
pp. 173-178
Author(s):  
Leon Green
Keyword(s):  
Pressure Drop ◽  
Heat Generation ◽  
Power Output ◽  
High Pressures ◽  
Temperature Stability ◽  
Porous Wall ◽  
Dimensionless Temperature ◽  
Temperature Profiles ◽  
Pumping Power ◽  
Thermal Dependence

Abstract A limiting case of solid-fluid heat transfer is examined, in which a gas passes through a porous wall of high specific surface with heat generation within the solid material. Dimensionless temperature profiles in the wall are presented in terms of the rate of heat generation, rate of flow, and thermal properties of the gas and solid. The pressure drop across the wall is approximated by using an average wall temperature and assuming isothermal conditions. Temperature profiles, pressure drops, and pumping-power/power-output ratios are calculated for the hypothetical case of a heated graphite wall cooled by helium. It is found that the thermal dependence of the gas viscosity produces a minimum in the pressure-drop versus flow-rate curve, and it appears that favorable pumping-power/power-output ratios can be obtained by the use of high pressures. The problem of temperature stability in a gas-cooled porous solid is pointed out and the need for experimental work emphasized. Use of the sweat-cooling technique for high-pressure, high-temperature ducts is suggested.

Investigation of Heat Transfer and Pressure Drop in a Porous Media with Internal Heat Generation

2021 ◽  
Author(s):  
Osama Hassan Hassan ◽  
Gamal Ibrahim Sultan ◽  
Ahmed Abdelsalam Hegazy ◽  
Mohamed Nabil Sabry
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Pressure Drop ◽  
Heat Generation ◽  
Internal Heat ◽  
Internal Heat Generation

Analysis of Heat Exchanger Concepts for Use As Gas Turbine Intercoolers

2001 ◽  
Author(s):  
Arash Saidi ◽  
Daniel Eriksson ◽  
Bengt Sundén
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Gas Turbine ◽  
Power Output ◽  
Heat Exchangers ◽  
Advantages And Disadvantages ◽  
Volume Weight ◽  
Different Types ◽  
Core Volume

Abstract This paper presents a discussion and comparison of some heat exchanger types readily applicable to use as intercoolers in gas turbine systems. The present study concerns a heat duty of the intercooler for a gas turbine of around 17 MW power output. Four different types of air-water heat exchangers are considered. This selection is motivated because of the practical aspects of the problem. Each configuration is discussed and explained, regarding advantages and disadvantages. The available literature on the pressure drop and heat transfer correlations is used to determine the thermal-hydraulic performance of the various heat exchangers. Then a comparison of the intercooler core volume, weight, pressure drop is presented.

scholarly journals OTEC Maximum Net Power Output Using Carnot Cycle and Application to Simplify Heat Exchanger Selection

Entropy ◽  
2019 ◽  
Vol 21 (12) ◽  
pp. 1143 ◽  
Author(s):  
Kevin Fontaine ◽  
Takeshi Yasunaga ◽  
Yasuyuki Ikegami
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Power Output ◽  
Heat Exchangers ◽  
Power Plants ◽  
Seawater Temperature ◽  
Carnot Cycle ◽  
Ocean Thermal Energy ◽  
Net Power Output

Ocean thermal energy conversion (OTEC) uses the natural thermal gradient in the sea. It has been investigated to make it competitive with conventional power plants, as it has huge potential and can produce energy steadily throughout the year. This has been done mostly by focusing on improving cycle performances or central elements of OTEC, such as heat exchangers. It is difficult to choose a suitable heat exchanger for OTEC with the separate evaluations of the heat transfer coefficient and pressure drop that are usually found in the literature. Accordingly, this paper presents a method to evaluate heat exchangers for OTEC. On the basis of finite-time thermodynamics, the maximum net power output for different heat exchangers using both heat transfer performance and pressure drop was assessed and compared. This method was successfully applied to three heat exchangers. The most suitable heat exchanger was found to lead to a maximum net power output 158% higher than the output of the least suitable heat exchanger. For a difference of 3.7% in the net power output, a difference of 22% in the Reynolds numbers was found. Therefore, those numbers also play a significant role in the choice of heat exchangers as they affect the pumping power required for seawater flowing. A sensitivity analysis showed that seawater temperature does not affect the choice of heat exchangers, even though the net power output was found to decrease by up to 10% with every temperature difference drop of 1 °C.

Laminar-Transitional Convection From Repeated Ribs in a Channel

1992 ◽  
Vol 114 (1) ◽  
pp. 29-34 ◽  
Author(s):  
R. A. Wirtz ◽  
Weiming Chen
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Three Dimensional ◽  
Electronic Packages ◽  
Average Heat Transfer Coefficient ◽  
Pumping Power ◽  
Low Profile ◽  
Linear Correlations ◽  
Transfer Pressure ◽  
Wall Spacing

Velocimetry, heat transfer, and pressure drop experiments are reported for laminar/transitional air flow in a channel containing rectangular transverse ribs located along one channel wall. The geometry is intended to represent an array of low profile electronic packages. At fixed pumping power per unit channel volume, the heat transfer rate per unit volume is independent of rib-to-rib spacing and increases with decreasing wall-to-wall spacing. The fully developed, rib-average heat transfer coefficient is found to be linearly related to the maximum streamwise rms turbulence measured above the rib-tops. Linear correlations, in terms of a descriptor of the rms streamwise turbulence, are shown to unify heat transfer/pressure drop data for channels containing either two-or three-dimensional protrusions.

Experimental Investigation of Crossflow Diverters in Jet Impingement Cooling

2019 ◽  
Author(s):  
Srivatsan Madhavan ◽  
Kishore Ranganath Ramakrishnan ◽  
Prashant Singh ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Turbine Blades ◽  
Jet Impingement ◽  
Target Surface ◽  
Pumping Power ◽  
Detailed Measurement ◽  
To Come

Abstract Jet impingement is a cooling technique commonly employed in combustor liner cooling and high-pressure gas turbine blades. However, jets from upstream impingement holes reduce the effectiveness of downstream jets due to jet deflection in the direction of crossflow. In order to avoid this phenomenon and provide an enhanced cooling on the target surface, we have attempted to come up with a novel design called “crossflow diverters”. Crossflow diverters are U-shaped ribs that are placed between jets in the crossflow direction (under maximum crossflow condition). In this study, the baseline case is jet impingement onto a smooth surface with 10 rows of jet impingement holes, jet-to-jet spacing of X/D = Y/D = 6 and jet-to-target spacing of Z/D = 2. Crossflow diverters with thickness ‘t’ of 1.5875 mm, height ‘h’ of 2D placed in the streamwise direction at a distance of X = 2D from center of the jet have been investigated experimentally. Transient liquid crystal thermography technique has been used to obtain detailed measurement of heat transfer coefficient for four jet diameter based Reynolds numbers of 3500, 5000, 7500, 12000. It has been observed that crossflow diverters protect the downstream jets from upstream jet deflection thereby maximizing their stagnation cooling potential. An average of 15–30% enhancement in Nusselt number is obtained over the flow range tested. However, this comes at the expense of increase in pumping power. Pressure drop for the enhanced geometry is 1–1.5 times the pressure drop for baseline impingement case. At a constant pumping power, crossflow diverters produce 9–15% enhancement in heat transfer coefficient as compared to baseline smooth case.

scholarly journals A Double-Bed Adsorptive Heat Transformer for Upgrading Ambient Heat: Design and First Tests

Energies ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 4037 ◽  
Author(s):  
Mikhail Tokarev
Keyword(s):  
Steady State ◽  
Heat Generation ◽  
Power Output ◽  
Thermal Efficiency ◽  
Natural Source ◽  
Specific Power ◽  
Specific Power Output ◽  
Heat Transformer ◽  
Continuous Heat ◽  
Steady State Cycling

A full scale lab prototype of an adsorptive heat transformer (AHT), consisting of two adsorbers, an evaporator, and a condenser, was designed and tested in subsequent cycles of heat upgrading. The composite LiCl/SiO2 was used as an adsorbent with methanol as an adsorbtive substance under boundary temperatures of TL/TM/TH = −30/20/30 °C. Preliminary experiments demonstrated the feasibility of the tested AHT in continuous heat generation, with specific power output of 520 W/kg over 1–1.5 h steady-state cycling. The formal and experimental thermal efficiency of the tested rig were found to be 0.5 and 0.44, respectively. Although the low potential heat to be upgraded was available for free from a natural source, the electric efficiency of the prototype was found to be as high as 4.4, which demonstrates the promising potential of the “heat from cold” concept. Recommendations for further improvements are also outlined and discussed in this paper.

Multi-Objective Design Optimization of Topology and Performance of Branching Networks of Cooling Passages

2006 ◽  
Author(s):  
Maickel Gonzalez ◽  
Ramon J. Moral ◽  
Thomas J. Martin ◽  
Debasis Sahoo ◽  
George S. Dulikravich ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Design Optimization ◽  
Total Pressure ◽  
Pareto Front ◽  
Total Heat ◽  
Pareto Optimal ◽  
Pumping Power ◽  
Multi Objective ◽  
Branching Networks ◽  
Number Of Branches

The objective of this study was to develop an automatic, self-sufficient, preliminary design algorithm for optimization of topologies of branching networks of internal cooling passages. The software package includes a random branches generator, a quasi 1-D thermo-fluid analysis code COOLNET, and multi-objective hybrid optimizer. COOLNET analysis software has the same trends as shown in an earlier publication depicting the results of a similar analysis code used by Pratt & Whitney. The hybrid multi-objective optimization code was verified against classical test cases involving multiple objectives. The number of branches per level was optimized in order to minimize coolant mass flow rate, total pressure drop, and maximize total heat removed. Optimization with four levels of fractal branching channel networks was tested. This optimization varied the number of branching channels extending from each single channel. COOLNET needed approximately forty iterations on average to analyze each configuration. The number of iterations necessary for each geometry depended on the number of branches per configuration. The hybrid multi-objective optimizer needed 500 iterations to create a converged Pareto front of optimized branching network configurations for the case of four branching levels. A population of 60 designs was used. The total number of function evluations analyzed was 30,000. The entire design optimization process takes approximately 3 hours on a single 3.0 GHz Pentium IV processor. In this work the total number of Pareto-optimal designs was 100. After finding the Pareto front points, the user has to decide which optimized cooling network configuration is the best for the desired application. It was demonstrated that this can be accomplished by utilizing Pareto-optimal solutions to create a curve representing pumping power vs. total heat removed and by observing which designs provide favorable break-even energy transfer. The magnitude of the ratio of heat transferred to total pressure drop and ratio of heat transfer to pumping power could be further increased by incorporating the channel’s hydraulic diameter, cross sectional area, lengths, and wall roughness as optimization variables.

Performance optimization for an open-cycle gas turbine power plant with a refrigeration cycle for compressor inlet air cooling. Part 1: Thermodynamic modelling

2009 ◽  
Vol 223 (5) ◽  
pp. 505-513 ◽  
Author(s):  
L Chen ◽  
W Zhang ◽  
F Sun
Keyword(s):  
Power Plant ◽  
Pressure Drop ◽  
Power Output ◽  
Working Fluid ◽  
Air Cooling ◽  
Refrigeration Cycle ◽  
Mixing Chamber ◽  
Compressor Inlet ◽  
Gas Turbine Power Plant ◽  
Flow Resistances

A thermodynamic model of an open cycle gas turbine power plant with a refrigeration cycle for compressor inlet air cooling with pressure drop irreversibilities is established using finite-time thermodynamics in Part 1 of this article. The flow processes of the working fluid with the pressure drops of the working fluid and the size constraints of the real power plant are modelled. There are 12 flow resistances encountered by the working fluid stream for the cycle model. Three of these, the friction through the blades, vanes of the compressor, and the turbines, are related to the isentropic efficiencies. The remaining flow resistances are always present because of the changes in the flow cross-section at the mixing chamber inlet and outlet, the compressor inlet and outlet, the combustion chamber inlet and outlet, the heat exchanger inlet and outlet, and the turbine inlet and outlet. These resistances associated with the flow through various cross-sectional areas are derived as functions of the mixing chamber inlet relative pressure drop, and they control the air flowrate and the net power output. The analytical formulae about the power output, efficiency, and other coefficients are derived with the 12 pressure drop losses. The numerical examples show that the dimensionless power output reaches its maximum at the optimal value and that the dimensionless power output and the thermal efficiency reach their maximum values at the optimal values of the compressor fore-stages pressure ratio of the inverse Brayton cycle.

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