Eight-Ton Advanced GAX Cycle Prototype Results
Abstract The advanced Vapor eXchange Generator Absorber heat eXchange (VX GAX) cycle has similar components as the basic GAX cycle but is a three-pressure cycle and makes more complete use of the GAX temperature overlap. Less external heat is supplied to the generator, and the cycle efficiency is increased. A breadboard prototype of a gas-fired heat pump using the VX GAX cycle has been developed and tested. A higher COP was achieved using reliable and cost effective components. This paper presents the VX GAX cycle breadboard design concept, the hardware realization, and the performance achieved. Several novel concepts were incorporated to achieve the design objectives of higher efficiency and capacity, lower cost, compactness, avoidance of code restrictions, and operability from 49°C (120°F) summer to −8°C (17°F) winter ambient conditions. The prototype results have confirmed the high performance capability of the advanced GAX cycle. At 35°C (95°F) ambient air-cooled conditions, a gas-cooling COP of 0.85 was achieved at design capacity. This is a 20% improvement relative to current basic GAX chillers. The eight-ton capacity is ideal for small-scale commercial applications and provides economy of scale. The wide ambient operating range is key to year-round operation and attractive payback in all climate zones. The demonstrated improvement in both system performance and cost is key to achieving nationwide mass-market status.