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Research Papers

# Enhancement of Temperature Blending in Convective Heat Transfer by Motionless Inserts With Variable Segment Length

[+] Author and Article Information
Ramin K. Rahmani

Department of MIME, The University of Toledo, Toledo, OH 43606rkhrahmani@yahoo.com

Anahita Ayasoufi

Department of Mathematics and Statistics, East Tennessee State University, Johnson City, TN 37614aayasoufi@yahoo.com

Department of Mechanical Engineering, Prince Mohammad Bin Fahd University, Al Khobar 31952, Kingdom of Saudi Arabiaemad-y-tanbour@hotmail.com

Hosein Molavi

Department of Mechanical Engineering, Tarbiat Modares University Tehran, 14115-111, Tehran, Iranhn.molavi@gmail.com

J. Thermal Sci. Eng. Appl 2(3), 031009 (Dec 22, 2010) (12 pages) doi:10.1115/1.4003087 History: Received July 16, 2010; Revised October 29, 2010; Published December 22, 2010; Online December 22, 2010

## Abstract

Stationary spiral inserts can effectively enhance heat transfer and temperature blending in the heat convection systems. In this paper, the impact of the segment length on the performance of a stationary insert is studied for flow Re numbers from $∼80$ to $∼7900$ through numerical simulation of heat transfer in streams of cold and hot gases flowing across it. The segment length to width ratio is from 1.11 to 2.33. The temperature of the studied gas is from 300 K to 1300 K. It is shown that the insert with variable segment length is more effective in temperature blending for two compressible streams compared with an insert with constant segment length, especially for low-Re-number turbulent flows.

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## Figures

Figure 3

Contours of temperature (K) at the leading and trailing edges of spiral insert variable segment length (Re=79)

Figure 4

Contours of temperature (K) at the trailing edge of spiral insert variabel segment length (Re=79)

Figure 5

Contours of temperature (K) at the trailing edge of spiral inserts (Re=790)

Figure 6

Contours of temperature (K) at the trailing edge of spiral inserts (Re=1976)

Figure 7

Contours of temperature (K) at the trailing edge of spiral inserts (Re=7903)

Figure 8

Standard deviation of temperature for gas flow across spiral motionless inserts at the insert trailing edge neighborhood (respectively for Re=79, 790, 1976, and 7903)

Figure 9

Temperature difference for gas flow across spiral motionless insert from the insert leading edge to insert trailing edge (Re=79)

Figure 10

Temperature difference for gas flow across spiral motionless inserts from the insert trailing edge neighborhood (respectively for Re=79, 790, 1976, and 7903)

Figure 11

Cross-sectional velocity vectors (colored by temperature (K)) for Re=79, left: with gap, right: no gap

Figure 1

(a) Spiral motionless inserts (from left to right: CSL, segment length increment of 25.4 mm (VSL1), and segment length increment ratio of 1.204 (VSL2)). (b) Left: opening in the spiral insert axis, right: gap between the spiral insert and the pipe.

Figure 2

Temperature contours from the leading edge to the trailing edge for the spiral insert with constant segment length of 152.4 mm (Re=79)

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