Compact Carbon-Carbon Composite Heat Exchanger

2002 ◽  
Author(s):  
M. Khairul Alam ◽  
Roland J. Watts ◽  
John Price
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
High Surface ◽  
Single Layer ◽  
Carbon Matrix ◽  
Carbon Composite ◽  
Metal Plate ◽  
Air Stream ◽  
Standard Plate ◽  
Composite Heat

Composite heat exchangers can provide significant reduction in the weight of a compact heat exchanger in comparison to metal heat transfer units. A Carbon-Carbon (C-C) composite heat exchanger core has been fabricated to study the heat transfer and friction characteristics of single layer plate-fin geometry. The plate and fins are both C-C composites, in which the carbon matrix is reinforced by high conductivity graphitic carbon fibers to improve the fin effectiveness of the heat exchanger. A heat flux is applied to the top and bottom of the heat exchanger core to heat an air stream passing through the channels. The heat transfer coefficient and the friction coefficient are determined and the experimental results are compared with data for a standard plate fin heat exchanger of similar geometry. It was determined that the C-C heat exchanger had lower Colburn heat transfer factor than a similar metal plate-fin heat exchanger; but had high surface temperature effectiveness. The friction factor of the C-C heat exchanger was slightly lower than the metal plate-fin heat exchanger.

Experiments and Modeling of a Mesoscale Laminar Plate Heat Exchanger

1999 ◽  
Author(s):  
Seung-Ho Hong ◽  
Vanessa Kenning ◽  
Charles Call ◽  
Reza Shekarriz
Keyword(s):  
Boundary Condition ◽  
Reynolds Number ◽  
Heat Exchanger ◽  
Periodic Boundary Condition ◽  
Periodic Boundary ◽  
Single Layer ◽  
Plate Heat Exchanger ◽  
Plate Heat ◽  
Layer Arrangement ◽  
Air Stream

Abstract In this paper, the results of an experimental and computational study on the development of a plate heat exchanger are presented and discussed. We have evaluated the characteristics of a miniature counterflow plate heat exchanger (PHE) using air as the working fluid. Because of the small characteristic channel dimension (Dh ≤ 1.9mm) and specific application of interest, the Reynolds number produced ranged between 20 < ReD < 1500, well within the laminar flow regime. The mass flow rates of the two hot and cold streams were maintained the same. Two different configurations were tested and modeled. The first configuration was the single-layer condition where one cold air stream was adjacent to another hot air stream in a counter-flow arrangement. The second configuration was the interleaved channel arrangement where the different layers alternate between cold and hot streams. Experiments were performed on a series of heat exchangers made of aluminum and stainless steel. The channel dimensions were 1mm × 20mm × 75mm. Because the flow region consists of hydrodynamically developing and fully developed flow for the range of Reynolds numbers tested, the experimental results show higher pressure drop compared with the results of fully developed parallel-plate channel flow and this difference increases with increasing Reynolds number. The dependency of Nusselt number on Reynolds number in the periodic boundary condition was larger than the single-layer arrangement. Further, the periodic boundary condition generates higher effectiveness than the single-layer arrangement. It was found that when using aluminum plates instead of stainless steel, axial conduction results in nearly 35% reduction in the overall heat transfer coefficient between hot- and cold-side channels. Computational results, corroborated with experimental data, suggested the use of an interleaved channel geometry for obtaining an effectiveness of 90% or higher when operating within the low mass flow rate regime.

Modeling of a Rotary Dry Cooling Tower

1981 ◽  
Vol 103 (4) ◽  
pp. 715-719 ◽  
Author(s):  
J. A. Valenzuela ◽  
L. R. Glicksman
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Cooling Tower ◽  
Thick Layer ◽  
Hot Water ◽  
Rotating Disks ◽  
Air Stream ◽  
Additional Resistance ◽  
Dry Cooling Tower ◽  
Dry Cooling

A novel design of a rotary heat exchanger to be used as a dry cooling tower is described. The heat exchanger consists of a matrix of thin steel disks which rotate between a hot water bath and a forced draft air stream. On top of the water floats a 2 cm thick layer of oil which coats the rotating disks and thus eliminates evaporation. An analytical model of the heat exchanger was developed and validated with experimental measurements taken on a 1.5 m dia test section. The model was then used to determine the net effect of the oil on the heat transfer performance. Although the oil film that coats the disks presents an additional resistance to the transfer of heat, it also contributes to the heat capacity of the disks. It was found that the reduction in the overall heat transfer rate due to the presence of the oil is small, of the order of 5 to 10 percent.

An Experimental Study on a Straight-Channel Printed Circuit Heat Exchanger for Supercritical CO2 Power Cycle Applications

2018 ◽  
Author(s):  
Aiwei Xu ◽  
Yanping Huang ◽  
Junfeng Wang
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
High Surface ◽  
High Surface Area ◽  
Straight Channel ◽  
Cold Side ◽  
Printed Circuit ◽  
Operation Parameters ◽  
Study Heat Transfer

A kind of compact plate-type heat exchanger, namely, Printed Circuit Heat Exchanger (PCHE) is one of the attractive options for S-CO2 Brayton Cycles, Because it can withstand higher temperature and pressure and has high surface-area-to-volume. The experiments were conducted for a NPIC straight-channel PCHE. In current study, we chose water as cold side fluid and S-CO2 as hot side fluid. Firstly, we fixed the cold side operation parameters to study heat transfer and pressure drop characteristics of the S-CO2 fluid side. Then we fixed the hot side operation parameters to study the pressure drop characteristics of the water side. Finally, existing heat transfer and friction correlations were used to compared with NPIC straight-channel PCHE experimental data and new correlations were developed.

Effect of Surface Roughness Induced by Laser Powder Bed Fusion Additive Manufacturing in a Mini-Channel Heat Exchanger

2019 ◽  
Author(s):  
T. Parent-Simard ◽  
A. Landry-Blais ◽  
P. K. Dubois ◽  
M. Picard ◽  
V. Brailovski
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Heat Exchanger ◽  
Gas Turbines ◽  
Low Cost ◽  
High Surface ◽  
Transfer Model ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed

Abstract The Inside-Out Ceramic Turbine (ICT) is a promising microturbine for aeronautics applications. To increase the cycle efficiency and reduce fuel consumption, microturbines must operate under the recuperated Brayton cycle. The addition of a heat exchanger (HEx) increases the weight of the engine and cancels out any fuel savings as compared to a non-recuperated turbine. For this reason, the requirements applied to HEx for aeronautic gas turbines are: low weight and volume, high effectiveness with a low pressure drop, capabilities to endure high pressure and temperature, and low cost. The Laser powder bed fusion (LPBF) opens a new design space for geometries that cannot be realized by conventional methods, but induces high surface roughness. This paper presents experimental and analytical studies of the influence of surface roughness on the performances of a 3D-printed, counterflow, mini-channel HEx, with 1% of the total mass flow rate of the ICT. Results showed that the friction and heat transfer are both increased in the the regime typically defined as laminar compared to the analytical results. The experimental results are in agreement with a 1D heat transfer model when using correlations for high-roughness values from the literature. LPBF is a promising method to manufacture gas turbine parts, but it is crucial to model and incorporate its manufacturing capacities in terms of precision and surface finish to enhance HEx heat transfer and potentially reduce mass.

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