​Abandoned heat pump system from mine water source for residential premises

Chinese researchers have developed an abandoned mine water heat pump system that can reportedly outperform residential gas boilers. It consists of a submersible pump, a plate heat exchanger, a water heat pump, a circulating water pump and an end section.

A group of scientists from Shandong Jianzhu University, China has developed a water heat pump heating system for residential spaces. The system can use hydrothermal resources from abandoned mine sites and is based on seasonal control as it provides only heating.

To enable proper deployment, the researchers explored a pump-and-feed well system for the system in an attempt to minimize the heat transfer phenomenon that can occur in both open-loop and closed-loop systems. "If the pumping wells are improperly located, the low-temperature water recharged into the aquifer can cause the water temperature in the pumping wells to fluctuate, which can reduce the efficiency of the source water heat pump," they said. . "This phenomenon associated with the change in water temperature in a particular pumping well due to backfilling is called heat transfer."

To find the optimal location, the scientists developed a numerical calculation model that took into account heat transfer and fluidity, among other conditions. For this model, 14 different well layouts were used, including three types with one pump well and one irrigation well, five types with one pump well and two irrigation wells arranged linearly, and six types with one pump well and two irrigation wells in a triangular shape. .

"A decrease in the pumping temperature of 0.5 K is called the critical point of heat transfer. When the pump temperature drops below 0.5 K, no heat transfer occurs, and when the pump temperature drops between 0.5 and 1 K, mild heat transfer occurs,” they explained. "When the temperature drops from 1 to 2 K, moderate heat transfer occurs. When the temperature drops by more than 2 K, there is a strong heat transfer."

Scientists simulated the operation of a heat pump system in a residential building in the Chinese city of Weifang and compared its performance with a gas boiler. The building had a peak heating load of 118.02 kW and a combined annual heating load of 153,486.91 kWh.

“The abandoned mine water source heat pump heating system is mainly composed of a submersible pump, a plate heat exchanger, a source water heat pump, a circulating water pump and an end section. Because the system is used only for heating," the academicians said.

The total energy consumption of the various systems was translated into standard coal consumption. According to the results, the mine water source heat pump heating system consumed 10,872 kg/h conventional coal, and the gas boiler heating system consumed 28,622.43 kg/h conventional coal. This represents a decrease of 17,750.43 kg, or 62.02%. CO2 emissions were reduced by 43,843.56 kg, SO2 by 355.01 kg, and dust by 177.50 kg.