A Multidisciplinary Capstone Senior Project: Interactive Cooling System

The aim of this paper is to present the design, development, and construction of an Interactive Cooling System (ICS) demonstration unit. This was accomplished by a multidisciplinary capstone senior design team consisted of three mechanical engineering students and two electrical engineering students was selected to work on this project and was supported by the industry. The design team was advised by two faculty members: one mechanical engineering and one electrical engineering. The unit demonstrates change phase as the refrigerant passes through the cold plate. The twophase process is visible and can be observed through the glass cover of the cold plate. The ICS is capable of cooling heat loads between 100 W to 1000 W and maintain the heated surface at a temperature of less than 100C. The performance of the ICS is described by presenting some experimental test data. This paper provides details about the design and development of the ICS, as well as testing and validation of this unit. Introduction Precision Cooling Division of Parker Hannifin Corporation has requested the development of an educational Interactive Cooling System (ICS). The purpose of this educational Interactive Cooling System is to demonstrate the versatility and capabilities of Parker’s Precision Cooling two-phase electronic-cooling technology. The two-phase cooling technology utilizes the heat of vaporization of a refrigerant in order to absorb excessive heat, commonly generated by a high powered electronic. The two-phase cooling technology is safer and more efficient method of heat transfer that reduces the weight, increases power density, and costs far less than the traditional heat sink or water cooling system. A multidisciplinary capstone senior design team consisted of three mechanical engineering students and two electrical engineering students was selected to work on this project. The team was advised by two faculty members: one mechanical engineering and one electrical engineering. It should be noted that this is not the first senior design multidisciplinary project that we advised. We had many more in the past. The students worked and communicated effectively as a team. They chose one of them to be the team leader to coordinate the design activities. The capstone senior design project spans two semesters. In the first semester, the P ge 2.74.2 problem statement is formulated and basic conceptual designs are generated and then evaluated. The best conceptual design is then selected and a complete and detailed design is generated by the end of the first semester. In the second semester, a prototype of the finished design is built, tested and evaluated. A final report and oral presentation to faculty and students are required from all design teams at the end each semester. It should be noted that there are six ABET Students Outcomes that are mapped to the course outcomes of this capstone senior design project. They are: (a) an ability to apply knowledge of mathematics, science, and engineering (c) an ability to design a system, component, or process to meet desired needs within realistic constraints such as economic, environmental, social, political, ethical, health and safety, manufacturability, and sustainability (d) an ability to function on single-discipline and multidisciplinary teams (e) an ability to identify, formulate, and solve engineering problems (g) an ability to communicate effectively (i) a recognition of the need for, and an ability to engage in life-long learning Based on the assessment that was conducted at the end of both semesters, all six Students Outcomes were highly achieved. The ICS is composed of the following components: cold plate, condenser, fan, pump, accumulator, piping, pressure sensors, temperature sensors, flow meter, R-134A refrigerant, fiberglass shell, aluminum frame, power supply, personal computer (PC), touchscreen monitor, data acquisition system (DAQ), and control algorithm. These components were researched, analyzed, modeled and selected to achieve specific performance criteria. The ICS was designed so that refrigerant would change phase as it passes through the cold plate. It was specified that this two-phase process must be visible, and the refrigerant must not enter a superheated state. The desired quality at the exit of the cold plate was set at 0.70. The ICS is capable of cooling of heat loads between 100 W to 1000 W and maintain the heated surface at a temperature of less than 100C. Precision Cooling Division of Parker Hannifin Corporation provided support to construct two ICS units. One unit is for Parker Hannifin Corporation to be used in technology trade shows to demonstrate the versatility and capabilities of Parker’s Precision Cooling two-phase electroniccooling technology . And the other unit is for our department of engineering to demonstrate thermodynamics processes and principles for our undergraduate mechanical engineering students. Such an apparatus would enhance the teaching (and learning) of thermodynamics. Students would be able to apply thermodynamics principles, such as the first and second laws, learned in the classroom lectures, to real-life problems. This approach could make the learning of thermodynamics a more pleasant experience for undergraduate mechanical engineering students. The Design Process and Specifications The design process that was employed in this research project is the one outlined by Bejan et al. and Jaluria. The first essential and basic feature of this process is the formulation of the problem P ge 2.74.3 statement. The formulation of the design problem statement involves determining the requirements of the system, the given parameters, the design variables, any limitations or constraints, and any additional considerations arising from safety, financial, environmental, or other concerns. Since the ICS is required to be designed as a demonstration unit, it needs to be portable and should meet the following specifications: Phase Composition: The liquid-vapor composition of the refrigerant must not reach a superheated-vapor state at any point in the ICS. Fan Speed: To expand upon the Parker Precision Cooling technology, the fan speed must be variable. The fan speed should be controlled based on feedback from the ICS. Maximum Weight: The maximum weight of the ICS is set at 500 lbs. This is a desired working specification that should be met in order to achieve a moveable interactive display. The ICS must have a robust structure and be transportable. Operating Temperature: The ICS must be able to function in a variety of ambient conditions. It must be fully functional in an atmosphere that has an air-temperature between 18 and 30C. The heat source surface exposed to the cold plate must be kept below 100 degrees Celsius. The ICS must be able to control the target temperature to ± 1C. Performance: The ICS must demonstrate cooling of heat loads between 100 W to 1000 W. Instrumentation: Every thermodynamic node in the ICS must contain property sensors (specifically to measure pressure and temperature). The ICS must contain control devices that will shut down the ICS in the event that the operating temperature is exceeded. The ICS should have the capability to export data to a PC in real time. Human Interaction: The ICS should allow for a significant amount of human interaction. The heat source and fan speed must be adjustable. The target temperature of the heat source, set by the user, must be within the achievable temperature range. There must be menus included in the interactive display so that the user can select different viewing options. After the problem statement was formulated, several conceptual designs were considered and evaluated. Each design concept was evaluated by the following criteria: Effectiveness, Cost, Safety, and Size. System Components 1. Thermodynamics Analysis To properly control the ICS, the thermodynamic system was analyzed. This analysis was required to properly size and select components such as the heat exchanger, the pump, the cold P ge 2.74.4 plate, and the fan. Figure 2 shows the thermodynamic schematic of two-phase cooling technology used in the development of the ICS. The selected refrigerant is R-134a. Fig. 2: Schematics of the thermodynamics two-phase cooling technology. 2. Cold Plate The copper cold plate, shown in Fig. 3, is the device that exchanges heat from the heat source to the fluid (refrigerant). The cold plate is mounted directly to the heat source. Thermal grease is applied between the cold plate and heat source to reduce the contact thermal resistance. A custom cold plate was designed by the team for the ICS. Fig. 3: Cold plate Page 2.74.5 The sight glass covering for the cold plate is made of tempered borosilicate glass. The thickness of glass for the ICS unit will be 1". The size will match the 3.5" by 7" dimensions of the cold plate. The manufacturing company of the glass provides a chart to assist in ordering the proper thickness of glass to withstand the pressure of the working fluid it is displaying and the unsupported length of the glass.