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RESEARCH PAPERS: Electronic Cooling

# The Electro-Adsorption Chiller: Performance Rating of a Novel Miniaturized Cooling Cycle for Electronics Cooling

[+] Author and Article Information
K. C. Ng

Mechanical Engineering Department, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260mpengkc@nus.edu.sg

M. A. Sai, A. Chakraborty

Mechanical Engineering Department, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260

B. B. Saha

Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga-koen, 6-1, Kasuga-shi, Fukuoka 816-8580, Japanbidyutb@cm.kyushu-u.ac.jp

S. Koyama

Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga-koen, 6-1, Kasuga-shi, Fukuoka 816-8580, Japankoyama@cm.kyushu-u.ac.jp

J. Heat Transfer 128(9), 889-896 (Feb 07, 2006) (8 pages) doi:10.1115/1.2241786 History: Received June 26, 2005; Revised February 07, 2006

## Abstract

The paper describes the successful amalgamation of the thermoelectric and the adsorption cycles into a combined electro-adsorption chiller (EAC). The symbiotic union produces an efficiency or COP (coefficient of performance) more than threefold when compared with their individual cycles. The experiments conducted on the bench-scale prototype show that it can meet high cooling loads, typically $120W$ with an evaporator foot print of $25cm2$, that is $5W∕cm2$ at the heated surface temperature of $22°C$, which is well below that of the room temperature. The COPs of the EAC chiller vary from 0.7 to 0.8, which is comparable to the theoretical maximum of about 1.1 at the same operating conditions. With a copper-foam cladded evaporator, the high cooling rates have been achieved with a low temperature difference. In addition to meeting high cooling rates, the EAC is unique as (i) it has almost no moving parts and hence has silent operation, (ii) it is environmentally friendly as it uses a nonharmful adsorbent (silica gel), and (iii) water is used as the refrigerant.

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## Figures

Figure 1

The dependence of the chip surface temperature versus the power intensity of CPU with a convective fins-fan system

Figure 2

A comparison of the simulated results of the electro-adsorption chiller (PEAC) versus the conventional methods of cooling the computer’s CPU

Figure 3

A schematic of the electro-adsorption chiller (EAC)

Figure 4

A pictorial view of the assembled bench-size electro-adsorption chiller (EAC)

Figure 5

Pictures of the key components of EAC prior to its assembly (all dimensions are in mm)

Figure 6

A schematic of the IR electric heaters with a kaleidoscope for uniform heat flux delivery at the evaporator

Figure 7

Temperature traces of the copper-foam cladded evaporator and the saturated vapor

Figure 8

The experimentally measured temporal history of the electro-adsorption chiller at a fixed cooling power of 120W: ◻ defines the temperature of reactor 1; ▴ indicates the silica gel temperature of reactor 2; ∘ shows the condenser temperature; ∎ represents the load surface (quartz) temperature and ——— is the evaporator temperature. Hence the switching and cycle time intervals are 100s and 600s, respectively.

Figure 9

Dühring diagram of the electro-adsorption chiller (EAC)

Figure 10

The dc profile of the EAC for a fixed terminal voltage of 23V of the thermoelectric modules. The current profiles for the forward polarity (switching and operation or the first half cycle) and the reversed polarity (very small time scale 700 to 1000s including switching and operation periods or the next cycle) are shown here.

Figure 11

Effects of cycle time on average load surface (quartz) temperature, evaporator temperature, and cycle average net COP. The constants used in this experiment are the heat flux qflux′4.7W∕cm2 and the terminal voltage of thermoelectric modules V=24V.

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