Design of a Bubble Pump Cooling System Demonstration Unit

Abstract

Abstract The aim of this study is to examine the feasibility of developing a bubble pump cooling system prototype that can dissipate a certain amount of heat generated by an insulated gate bipolar transistor. To this end, a bubble pump cooling system prototype was designed and developed. The performance of the bubble heat pump cooling system prototype is described by presenting some experimental test data. This paper provides details about the design and development of the heat pump cooling system prototype, as well as testing and validation of this unit. Keywords: Bubble Pump, Design, Cooling System 1. Introduction Several methods in which vapor bubbles or gas can be used for the pumping of liquids are described in the literature [1-8]. Bubble pumps or air-lift pumps are devices that raise a liquid using vapor bubbles or compressed air, or in general raise a liquid by introducing bubbles into the outlet tube. The hydrostatic principle is used to create the required pressure difference between the pressure in the outlet tube and the pressure at the tube opening. The hydrostatic pressure in the outlet tube is reduced versus the hydrostatic pressure at the tube opening. The bubble pump depends on the saturation temperature (i.e., boiling point) of the working fluid for its operation. A thermally driven bubble pump that can be powered by solar thermal energy or waste heat can be used to lift the liquid solution without any mechanical moving part. Pfaff et al. [9] carried out both analytical and experimental studies on bubble pump. A test rig was built in glass to examine the performance of the bubble pump, to visualize the flow regime and to validate the analytical model. Several studies [10-15] have examined the performance of the bubble pump for diffusion absorption cooling machines and refrigeration units. Precision Cooling Division of Parker Hannifin Corporation has requested the development of a bubble pump cooling system demonstration unit. The bubble pump cooling system will be used to show potential customers of Parker Hannifin Corporation, their ability to develop a system that can dissipate heat from an insulated gate bipolar transistor (IGBT). This bubble pump will be driven independently of any other power source and will operate from the thermal energy losses of the IGBT. A schematic of the cooling system is shown in Fig. 1. This cooling system‟s cycle operates with a fluid that is heated to two-phase and is driven by the bubble pump. The bubble pump cooling system works by maintaining the fluid near the saturated state and when introduced to a heat source it begins to boil. Vapor bubbles in the boiling fluid increase in size as the quality or the amount of vapor increases and becomes more buoyant than the liquid causing them to rise. The vapor bubbles rise upward through a tube with an inside diameter equivalent to the diameter of the vapor bubbles such that liquid is trapped and lifted between vapor bubbles generating flow. The two-phase fluid is then condensed back to a saturated or slightly sub-cooled liquid by rejecting heat to the surroundings. This paper provides details about the design and development of the bubble pump cooling system prototype, as well as testing and validation of this unit.