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Heating buildings with air source heat pumps (ASHPs) has the potential to save energy compared to utilizing conventional heat sources. Accurate understanding of the efficiency of ASHPs is important to maximize the energy savings. While it is well understood that, in general, ASHP efficiency decreases with decreasing outdoor temperature, it is not well understood how the ASHP efficiency changes with different levels of thermal loading, even though it is an important consideration for sizing and controlling ASHPs. The goal of this study was to create an empirical model of the ASHP efficiency as a function of two independent variables–outside temperature and level of thermal loading. Four ductless mini-split ASHPs were evaluated in a cold chamber where the temperature (representing the outdoor temperature) was varied over a wide range. For each temperature, the ASHP performance data were collected at several levels of thermal loading. The data for all four ASHPs were combined and approximated with an analytical function that can be used as a general model for the ASHP steady-state efficiency as a function of the outside temperature and level of thermal loading. To the knowledge of the authors, no such empirical model that is solely based on third-party test data has been published before. While limitations exist, the model can be used to help guide future selection and operation of ASHPs.
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Thermal mapping of Hollow Cathodes to model the thermal loads of Iodine Ion Propulsion
Iodine possesses desirable qualities that could make it a potential fuel of choice in future space missions requiring ion propulsion, potentially replacing Xenon; if the thruster can have similar endurance despite Iodine's corrosiveness. A computer-aided design model of a hollow cathode with a Lanthanum Hexaboride insert was created in Solidworks, using its thermal load simulator to generate an approximate temperature model of it in operation. Data was then collected to refine the model by getting temperature readings of a hollow cathode in operation by attaching type K thermocouples to the outside and inside of the hollow cathode and firing it in a vacuum chamber. Differences between the thermal model and the experimental data will be discussed in addition to the assumptions made within the thermal model. Based on the data, the hollow cathode is far below expected temperatures, though there are several sources of error to explain this discrepancy.
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- Award ID(s):
- 1655280
- PAR ID:
- 10232066
- Date Published:
- Journal Name:
- 72nd Annual Meeting of the APS Division of Fluid Dynamics
- Volume:
- 64
- Issue:
- 13
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Conference Paper:
- The DOI is not currently available.
