PERFORMANCE EVALUATION OF CITRIC - ION STABILIZES
MAGNETIC FLUID HEAT PIPE.
Balachandran Jeyadevan, Hiroyuki Jeyadevan, Katsuto
Nakatsuka
Graduate
Schoole of Enviromental Studies, Tohoku University, Sendai 980 – 8579, Japan
Introduction
The development of heat
exchangers to sink the heat dissipated from industrial processes and
miniaturezed equipments 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-cjndensed gas at elevated temperaturees, Furthemore, the heat
pipe with CMF as working liquid showed 13 % enchancement 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 simolar 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 cp 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[ut power was enchanced by 13 % under an applied magnetic field,
similar behavior was not confirmed at higher input power. And also, the
enchancement 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.
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.