Modeling and design of a power boosted turbo-compression cooling system
Date
2021
Authors
Roberts, Nickolas Richard, author
Bandhauer, Todd M., advisor
Quinn, Jason C., committee member
Cale, James, committee member
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Abstract
Waste heat recovery technologies have the potential to reduce fuel consumption and address increased electricity and cooling demands in shipboard applications. Existing thermally driven power and cooling technologies are simply too large to be installed on ships where space for new equipment is extremely limited. This study addresses major shipboard challenges through the modeling and design of a volume optimized turbo-compression cooling system (TCCS). The TCCS is driven by low-grade waste heat in the shipboard diesel generator set jacket water and lubrication oil and was designed to be a drop-in replacement of electric chiller systems. A case study of a marine diesel generator set and electric chiller is presented, including annual engine loading and seawater temperature profiles. Three TCCS integration options and five working fluids (R134a, R1234ze(E), R1234yf, R245fa, R515a) were evaluated over the range of case study conditions using a fixed heat exchanger effectiveness thermodynamic model. The hybrid thermally and electricity driven "power boosted" TCCS reduced electricity consumption for cooling by over 100 kWe. Plate and frame heat exchanger models were used to size and optimize the system to fit within the volume of a commercial centrifugal chiller of equal cooling capacity. The system used R134a, provided 200-tons of cooling, and had an electric coefficient of performance (COP) of 9.84 at the design conditions. Optimized heat exchanger and pipe geometries were fixed, and the model was run over the range of case study conditions to determine annual fuel savings of 92.1 mt yr-1 and a weighted average generator set power density improvement of 11.0%. Heat exchangers, turbomachinery, and piping were solid modeled to demonstrate that the system fits within the required footprint (40.6 ft2) and volume (267 ft3). The designed system was estimated to cost $295,036 in equipment and $442,554 in total installed costs. The resulting payback period was 5.77 years while operating for only 3,954 hours per year. Over a 15-year period, the net present value and internal rate of return were $176,734 and 16%, respectively.
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Subject
ORVC
TCCS
waste heat recovery
shipboard
organic Rankine cycle
vapor compression cycle