Experimental heating performances of a ground source heat pump (GSHP) for heating road unit

Abstract

• A full-scale road heating system was implemented in Harbin. • Performances of ground source heat pump were evaluated. • Road heating performances were analyzed. • Effects of supplied water temperature and flow rate were investigated. A ground source heat pump (GSHP) was implemented in Harbin (the coldest provincial capital of China) for heating a road unit, which was comprised of two 2.5 m × 5.0 m road bases (one with the 200 mm tube-pitch and the other with the 300 mm tube-pitch). The heating performances of the system including supplied water temperature, road surface temperature and system COP (coefficient of performance) as affected by the set water temperature (25, 30 and 35 °C) and flow rate (2, 3 and 4 m 3 /h) were investigated. The results indicated that it took 13, 45 and 85 min to reach the set water temperatures of 25, 30 and 35 °C, respectively. For a heating time of 5 hours, the road surface temperatures were increased in the ranges of −10.56 to −4.37 °C, −10.54 to −3.95 °C and −12.25 to −2.78 °C using the 200 mm tube-pitch road base compared to −12.02 to −6.69 °C, −12.30 to −5.88 °C and −13.05 to −4.33 °C using the 300 mm tube-pitch road base, and the average system COPs were 3.01, 1.97 and 1.92, when the set water temperatures were 25, 30 and 35 °C, respectively. When the set water flow rates were 4, 3 and 2 m 3 /h, it took 45, 30 and 20 min to reach the set water temperature of 30 °C, respectively. For a heating time of 5 hours, the road surface temperatures were increased in the ranges of −10.54 to −3.95 °C, −9.02 to −0.03 °C and −8.10 to −4.51 °C using the 200 mm tube-pitch road base, and the average system COPs were 1.97, 2.62 and 2.22 when the set water flow rates were 4, 3 and 2 m 3 /h, respectively. The results presented in this study offer a good reference for the design of GSHP heating road systems in severely cold regions.