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Research Papers: Micro/Nanoscale Heat Transfer

# The Effects of Working Fluid on the Heat Transport Capacity of a Microheat Pipe

[+] Author and Article Information
D. Sugumar

Center for Material and Fiber Innovation, Deakin University, Waurn Ponds, 3217 Victoria, Australiasdhar@deakin.edu.au

Kek-Kiong Tio

Faculty of Engineering and Technology, Multimedia University, Bukit Beruang, 75450 Melaka, Malaysiakktio@mmu.edu.my

J. Heat Transfer 131(1), 012401 (Oct 20, 2008) (10 pages) doi:10.1115/1.2977547 History: Received January 21, 2008; Revised May 15, 2008; Published October 20, 2008

## Abstract

The effects of the thermophysical properties of the working fluid on the performance of a microheat pipe of triangular cross section are investigated. For this purpose, five different working fluids are selected: water, hepthane, ammonia, methanol, and ethanol. For operating temperatures ranging from $20°Cto100°C$, it is found that the behavior of the heat transport capacity is dominated by a property of the working fluid, which is equal to the ratio of the surface tension and dynamic viscosity $σ∕μl$. This property has the same dimension as velocity and can be interpreted as a measure of the working fluid’s rate of circulation, which can be provided by capillarity after overcoming the effect of viscosity. Of the five working fluids selected, ammonia is preferable for operating temperatures below $50°C$ since it yields the highest heat transport capacity; however, water is the preferred working fluid for temperatures above $50°C$.

###### FIGURES IN THIS ARTICLE
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Copyright © 2009 by American Society of Mechanical Engineers
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## Figures

Figure 9

Heat transport capacity, as a function of the operating temperature, of the equilateral-triangle MHP in Table 1 for different angles of inclination. Here, the working fluid is water.

Figure 10

Heat transport capacity, as a function of the operating temperature, of the equilateral-triangle MHP in Table 1 for different angles of inclination. Here, the working fluid is hepthane.

Figure 11

Heat transport capacity, as a function of the operating temperature, of the equilateral-triangle MHP in Table 1 for different angles of inclination. Here, the working fluid is ammonia.

Figure 13

Heat transport capacity, as a function of the operating temperature, of the equilateral-triangle MHP in Table 1 for different contact angles. Here, the working fluid is ammonia.

Figure 1

(a) A schematic of an inclined microheat pipe, θ being the angle of inclination; (b) cross-sectional view of a triangular MHP, showing the onset of flooding

Figure 2

Heat transport capacity, as a function of the operating temperature, of the equilateral-triangle MHP in Table 1 optimally filled with different types of working fluid

Figure 3

The integral in Eq. 20 for different types of working fluid, as a function of their temperature

Figure 4

Ratio of surface tension and liquid dynamic viscosity of different types of working fluid, as a function of their temperature

Figure 5

Latent heat of evaporation per unit volume for different types of working fluid, as a function of their temperature

Figure 6

Optimal charge level, as a function of the operating temperature, for the equilateral-triangle MHP in Table 1 filled with different types of working fluid

Figure 7

Optimal mass of the working fluid, as a function of the operating temperature, for the equilateral-triangle MHP in Table 1 filled with different types of working fluid

Figure 8

Gravity number Ga of different types of working fluid, as a function of the operating temperature.

Figure 12

Heat transport capacity, as a function of the operating temperature, of the equilateral-triangle MHP in Table 1 for different contact angles. Here, the working fluid is water.

## Errata

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