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Heat Exchangers

Enhanced Design of Cross-Flow Microchannel Heat Exchanger Module for High-Performance Aircraft Gas Turbine Engines

[+] Author and Article Information
Brittany Northcutt

Boiling and Two-Phase Flow Laboratory (BTPFL),  Purdue University International Electronic Cooling Alliance (PUIECA), Mechanical Engineering Building, 585 Purdue Mall, West Lafayette, IN 47907;  Rolls-Royce Purdue University Technology Center (UTC), Maurice Zucrow Laboratories, 500 Allison Road,  Purdue University, West Lafayette, IN 47907mudawar@ecn.purdue.edu

Issam Mudawar1

Boiling and Two-Phase Flow Laboratory (BTPFL),  Purdue University International Electronic Cooling Alliance (PUIECA), Mechanical Engineering Building, 585 Purdue Mall, West Lafayette, IN 47907;  Rolls-Royce Purdue University Technology Center (UTC), Maurice Zucrow Laboratories, 500 Allison Road,  Purdue University, West Lafayette, IN 47907mudawar@ecn.purdue.edu

1

Corresponding author.

J. Heat Transfer 134(6), 061801 (May 08, 2012) (13 pages) doi:10.1115/1.4006037 History: Received May 18, 2011; Revised November 28, 2011; Published May 08, 2012; Online May 08, 2012

This study explores the design of highly compact air–fuel heat exchangers for high-performance aircraft turbine engines. The heat exchangers consist of a large number of modules that can be brazed together into a rectangular or annular outer envelope. Inside the module, fuel flows through parallel microchannels, while air flows externally perpendicular to the direction of the fuel flow over rows of short, straight fins. A theoretical model recently developed by the authors for a single module is both validated experimentally, by simulating aircraft fuel with water, and expanded to actual heat exchangers and JP-8 aircraft fuel. An optimization study of the module’s geometrical parameters is conducted for high-pressure-ratio engine conditions in pursuit of the highest heat transfer rate. These parameters are then adjusted based on such considerations as microfabrication limits, stress and rupture, and the need to preclude clogging of the fuel and air passage. Using the revised parameters, the analytical model is used to generate effectiveness plots for both rectangular and annular heat exchangers with one air pass and one, two, or three fuel passes. These results demonstrate both the effectiveness of the module design and the versatility of the analytical tools at designing complex heat exchangers for high-performance aircraft gas turbine engines.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

(a) Cross-flow microchannel air–fuel heat exchanger module, (b) rectangular heat exchanger configuration (shown with one air pass and three fuel passes), and (c) annular heat exchanger configuration (shown with one air pass and two fuel passes)

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Figure 2

Test module: (a) side view depicting fuel microchannel dimensions and profiles of airside fins and (b) top view depicting rows of airside fins. (c) Various photos of test module

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Figure 3

Schematics and nomenclature of: (a) overall model for cross-flow microchannel heat exchanger module with uniform inlet fluid temperatures, (b) test module, (c) finned airside boundary, and (d) fuel microchannels and unfinned airside boundaries

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Figure 4

Equivalent thermal resistance network representing: (a) entire microchannel test module and (b) symmetrical module design used in actual heat transfer analysis

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Figure 5

Comparison of unit cell boundary conditions for: (a) experimental module, (b) module in rectangular heat exchanger, and (c) module in annular heat exchanger

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Figure 6

Percent error in predicting airside and waterside temperature drop with water flow rate for: (a) m·h = 0.00553 kg/s, Th,i  = 90.5 °C, and Tc,i  = 24.3 °C, (b) m·h = 0.0069 kg/s, Th,i  = 93.6 °C, and Tc,i  = 24.4 °C, and (c) m·h = 0.0097 kg/s, Th,i  = 69.0 °C, and Tc,i  = 24.1 °C

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Figure 7

Variation of normalized temperature difference with: (a) airside fin width, (b) airside channel width, (c) airside fin length, (d) fuel microchannel width, and (e) fuel microchannel wall thickness

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Figure 8

Variation of normalized temperature difference with: (a) airside fin height, (b) fuel microchannel height, (c) module’s outer wall thickness, (d) number of airside fins rows for constant airside channel width, and (e) number of fuel microchannels for constant microchannel width

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Figure 9

Effectiveness results for: (a) rectangular heat exchanger with one air pass and one, two, and three fuel passes and (b) annular heat exchanger with one air pass and one, two, and three fuel passes

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