Performance evaluation of citric-ion stabilizes magnetic fluid heat pipe

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.