June 18, 2006
June 18, 2006
June 21, 2006
Energy Conversion and Conservation
11.461.1 - 11.461.11
Development of a Virtual Refrigeration Apparatus to Promote Understanding of the Actual Experiment
Abstract A numerical simulation of an existing vapor compression refrigeration experiment has been created. This simulation can be used prior to lab to familiarize students with both the equipment and the phenomena. The fidelity of the interface toward duplicating the actual controls is intended to give students a basic understanding of how to operate the equipment when they arrive at lab. The modeled equations are intended to represent actual system variables allowing students to explore various behaviors of the system without having to worry about safety issues or harm to the system. This paper will describe how the program has been created within the LabVIEW environment. The assumptions which are employed and those which are allowed to be violated will be detailed as well as the resulting governing equations. Current performance of the “virtual refrigerator” will be discussed as well as the challenges in creating such a program.
Students in Mechanical Engineering often are required to take several experimentation courses covering the breadth of the curriculum. The experiments related to the thermal-fluid sciences generally include topics related to thermodynamic cycles and energy use. These experiments can encompass very non-linear and coupled phenomena. Subsequently, they can often be very time consuming to perform and difficult for the students to initially grasp. One such experiment is the study of a vapor compression refrigeration cycle. Adjusting one cycle parameter often induces changes in several others. It is common for students to operate the cycle in a way which violates standard cycle assumptions or which can create safety hazards.
For a laboratory instructor this creates three problems. First, students will take longer to perform the experiment as they struggle with the equipment. Second, students and equipment may be put at risk. Third, student comprehension and educational impact is reduced. To address these issues the LabVIEW software package has been used to create a virtual representation of a basic refrigeration experiment for use as a pre-lab exercise. This form of simulation has become more widely used as virtual experimentation has come of age1,2.
This paper will describe the programming structure and such key components as thermodynamic property calculation. The assumptions that are employed and those that are not enforced will be detailed as well as the resulting governing equations. Methods of incorporating these into LabVIEW will be highlighted. The current version of the software does not meet all of the expectations. Therefore, plans for future modifications will be detailed and justified.
II. Description of Refrigeration Experiment
The refrigeration apparatus under study (Figure 1) was designed and manufactured in 2003 as part of an ASHRAE funded Senior Design Project. The system uses a typical vapor compression cycle with R-134a as the refrigerant. For the compressor, a Seltec TM-08 unit was used. This
Tebbe, P. (2006, June), Development Of A Virtual Refrigeration Apparatus To Promote Understanding Of The Actual Experiment Paper presented at 2006 Annual Conference & Exposition, Chicago, Illinois. https://peer.asee.org/351
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