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Heat Exchangers

Hydrocarbon Refrigerant Vaporization Inside a Brazed Plate Heat Exchanger

[+] Author and Article Information
Giovanni A. Longo

Department of Management and Engineering,  University of Padova, Str.lla S. Nicola No. 3, I-36100 Vicenza, Italytony@gest.unipd.it

Color representation of Figs. 6 through 8 can be found in the online publication of this paper.

J. Heat Transfer 134(10), 101801 (Aug 14, 2012) (10 pages) doi:10.1115/1.4006817 History: Received November 06, 2011; Revised May 03, 2012; Published August 13, 2012; Online August 14, 2012

This paper presents the experimental heat transfer coefficients and pressure drop measured during HC-600a (isobutane), HC-290 (propane), and HC-1270 (propylene) vaporization inside a brazed plate heat exchanger (BPHE): the effects of heat flux, refrigerant mass flux, saturation temperature (pressure), evaporator outlet condition, and fluid properties are investigated. The experimental tests include 172 vaporization runs carried out at three different saturation temperatures (10, 15, and 20 °C) and four different evaporator outlet conditions (outlet vapor quality around 0.80 and 1.00, outlet vapor super-heating around 5 and 10 °C). The refrigerant mass flux ranges from 6.6 to 23.9 kg m−2 s−1 and the heat flux from 4.3 to 19.6 kW m−2 . The heat transfer and pressure drop measurements have been complemented with IR thermography analysis in order to quantify the portion of the heat transfer surface affected by vapor super-heating. The heat transfer coefficients show great sensitivity to heat flux, evaporator outlet condition and fluid properties and weak sensitivity to saturation temperature (pressure). The frictional pressure drop shows a linear dependence on the kinetic energy per unit volume of the refrigerant flow and therefore a quadratic dependence on refrigerant mass flux. HC-1270 exhibits heat transfer coefficients 6–12% higher than HC-290 and 35–50% higher than HC-600a and frictional pressure drops 5–10% lower than HC-290 and 60% lower than HC-600a. The experimental heat transfer coefficients are compared with two well-known correlations for nucleate boiling and a linear equation for frictional pressure drop is proposed.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic view of the experimental test rig

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Figure 2

Schematic view of the plate

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Figure 3

Average heat transfer coefficient on refrigerant side versus heat flux: HC-600a

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Figure 4

Average heat transfer coefficient on refrigerant side versus heat flux: HC-290

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Figure 5

Average heat transfer coefficient on refrigerant side versus heat flux: HC-1270

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Figure 6

IR thermography of the BPHE during HC-600a vaporization tests at 10 °C of saturation temperature with 9 kWm−2 of heat flux

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Figure 7

IR thermography of the BPHE during HC-290 vaporization tests at 10 °C of saturation temperature with 9 kWm−2 of heat flux

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Figure 8

IR thermography of the BPHE during HC-1270 vaporization tests at 10 °C of saturation temperature with 9 kWm−2 of heat flux

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Figure 9

Saturated boiling experimental data versus Thonon [17] criterion

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Figure 10

Comparison between experimental and calculated saturated boiling heat transfer coefficient by Cooper [18]) equation

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Figure 11

Comparison between experimental and calculated saturated boiling heat transfer coefficient by Gorenflo [19] equation

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Figure 12

Saturated boiling frictional pressure drop versus refrigerant mass flux

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Figure 13

Saturated boiling frictional pressure drop versus kinetic energy per unit volume

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