Abstract
Vuilleumier machines are a promising technology for heating. Respective performances of Vuilleumier’s engine and cooler are generally unclear. In Stirling machines, performances can be determined based on PV power flow and heat flow methods. In this work, respective performances based on two methods in current Vuilleumier models were investigated. It was found that PV power flow and heat flow methods in current Vuilleumier models were ineffective for analysis of respective performances due to there being no piston as a boundary between Vuilleumier’s engine and cooler. Then, a virtual piston was assumed, and a virtual piston based Vuilleumier model (VPBVM) was developed. The relative Carnot efficiencies of the obtained engine and cooler were 53~64% and 43~49%, respectively, at conditions of 550 °C hot temperature, 50~70 °C warm temperature, and −20~10 °C cold temperature. The results indicated that respective performances obtained in VPBVM were reasonable. Moreover, the engine’s compression ratios could be obtained in VPBVM and were 1.2~1.24. Thus, VPBVM could be effective for the analysis of the Vuilleumier machine’s engine and cooler.
Highlights
Vuilleumier machines are a promising technology for heating [1,2]
As thermal-to-mechanical efficiency in the independent Stirling engine and mechanical-to-thermal efficiency in the independent Stirling cooler can reach 68% [5] and 41~46% [6] of Carnot efficiency, respectively, Vuilleumier machines could have 28~31% of Carnot efficiency for cooling, which is the product of the independent Stirling engine and independent Stirling cooler values [7]
Energies 2021, 14, 5923 practical Vuilleumier machines is only 15%, which is nearly half of the value based on an independent Stirling engine and independent Stirling cooler
Summary
Vuilleumier machines are a promising technology for heating [1,2]. Figure 1 shows a schematic diagram of free piston Vuilleumier machines, which consist of displacers (hot Dh and cold Dc), regenerators (hot 5 and cold 8 ), chambers (hot 1 , warm 2 and cold 3 ), and heat exchangers (hot 4 , hot-warm 6 , cold-warm 7 , and cold 9 ). Power flow and heat flow will be effective in the performance analysis of Vuilleumier’s hypothetical Stirling engine and Stirling cooler. The effectiveness of PV power flow and heat flow methods in the performance analysis of Vuilleumier’s hypothetical Stirling engine and cooler should be evaluated. The method for tracking the virtual piston’s position during the cycle needs to be studied In this work, both PV power flow and heat flow methods were first employed for the analysis of hypothetical Stirling engine’s and Stirling cooler’s performance in current Vuilleumier models. Respective performances of the hypothetical Stirling engine and cooler were obtained and analyzed based on the developed virtual piston model
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