PERFORMANCE EVALUATION OF CITRIC - ION STABILIZES
MAGNETIC FLUID HEAT PIPE.
Balachandran Jeyadevan, Hiroyuki Jeyadevan, Katsuto
Nakatsuka
Graduate
School of Environmental Studies, Tohoku University, Sendai 980 – 8579, Japan
Introduction
The development of heat
exchangers to sink the heat dissipated from industrial processes and
miniaturized equipment’s is being intensively researched. Though considerable
progress has been made in macro devices, the control of heat transfer in micro
devices is still a challenge. Thus with the idea of enhancing the working
liquid [1,2]. The citrate ion-stabilized magnetic fluid (CMF) was stable and
free of any non-condensed gas at elevated temperatures, Furthermore, the heat
pipe with CMF as working liquid showed 13 % enhancement in heat transfer
compared to the field free case [3]. However, a detailed study was yet to be
carried out. Therefore, the aim of this research work is to study the
performance of a heat pipe using citric ion-stabilized water-based MF as the working
liquid in magnetic field and compare the same with that of the heat pipe using
water as the working liquid.
Experiment
The CMF heat pipe consisted
of heating, adiabatic, and condenser sections. The experimental set up is
similar to the one shown in reference 3. Temperatures at different sections
were measured at the wall of the Cu pipe. The magnetic field was applied using
a Nd-Fe-B permanent magnet. In addition to JC-1 with magnetization, solid
concentration and viscosity of 16,4 emu / g, 33.6 wt . % and 6.5 centipoise
respectively, CMF with a solid concentration of 28.2 % was also used. The heat
transfer characteristics as a function of magnetic field strength and
distribution were studied by using different magnet configurations.
Results and discussion.
First, the operating
temperature range of the heat pipe was studied by varying the temperature of
the heat source between 120 and 180°C. Though the heat transfer
at lower in power was enchanted by 13 % under an applied magnetic field, similar
behavior was not confirmed at higher input power. And also, the enhancement in
heat transfer at lower input power was not observed after operating at higher
temperatures, To investigate the reason, the pipe was cut open and the solid
particles were analyzed to find that the magnetite has transformed
into-hematite. To study the stability conditions of magnetite, water-magnetite,
water-citrate ion-magnetite, and citrate ion stabilized magnetic fluid systems
were introduced into a stainless steel pipe and heated in an oven at 120, 140,
160, and 185°C for 12 hours, 1 day, 2
days, 1 week and 2 weeks. Though the dispersed particles were stable within the
temperature range of 120 and 160C, the magnetite transformed to hematite at
temperatures above 160C. The performance of the heat pipe with magnetic fluid
as the working liquid was evaluated under different magnetic field
configuration. Under an optimum magnet configuration the heat transfer was
enhanced by 30 % compared to the field-free case.
Then, the heat transfer
characteristic of the magnetite fluid heat pipe under an optimum magnetic field
strength and distribution was compared with the heat pipe using water as the
working liquid. The transferred heat in heat pipe using CMF was enhanced by a
maximum of 10% over water in temperature range of 118 – 130°C as shown in Figure 1. The heat
transfer in MCF heat pipe under different magnetic field strength and
distribution will also be discussed.
Figure
1.
The
relation between heat flux and heat transferred
in
heat pipe using (a) MCF and (b) water as working liquid.
References:
1.
Nakatsuka
K., Hama Y., Takahashi J. // J. Magn. Magn. Mat. 85 (1990) 207 – 209.
2.
Yamashite
N., Takahashi J., Nakatsuka K. // Japan society of magnetic fluid research,
1991, P. 43.
3.
Nakatsuka
K., Jeyadevan B., Neveu S., Koganezawa H. // J. Magn. Magn. Mat. 252 (2002) 360 – 362.