Brief Analysis of Difference between Direct Heat Pump and Circulating Heat Pump

Direct heating method, a simple understanding is that cold water from the outside world after entering the heat pump unit is 60 ℃ hot water, but there is no small water tank inside the device. As there is no circulating pump between the holding tank and the equipment, the opening and stopping of the equipment is controlled in full accordance with the water level controller of the tank. Direct thermal advantages are reflected in the following areas: No need for circulating pumps, reduce energy consumption and failure probability. Get a steady stream of hot water around 60 ℃, do not need to wait, make up water faster than the cycle, encountered a large amount of customers, higher safety factor. Without any auxiliary heating equipment, the water temperature can reach 65 ℃. Condensation system within the device to run under 20 kg pressure, reducing the system high pressure, the compressor at light load operation, extend compressor life. Direct thermal equipment is a direct hot water to the hot water tank, even in the event of peak water consumption, customer water temperature without any impact. Insulation tank size reduced by 30%. Due to the direct replenishment of hot water, even if the user runs out of water in the insulated water tank, the temperature of the water in the water tank is maintained at about 60 ° C, so that it can be utilized 100%. Circulating heating due to make up cold water, when faced with a lot of water, the tank temperature dropped significantly, the tank temperature has dropped below 40 ℃. In order to ensure user requirements, often the solution is to increase the tank volume. Direct heat heat pump water heater, low temperature tap water directly absorbs the heat of high temperature refrigerant, so that the refrigerant is fully cooled, the system pressure is reduced, the compressor to overcome the system pressure consumed less energy to extend compressor life, unit operating efficiency High-cycle heating, summed up in two ways: First: First, all the water tank filled with cold water, water pump through the circulating pump water into the heat pump host heating. In general, each cycle can raise the temperature of water about 10 ℃. For example, we now want to heat the water at a temperature of 20 ° C to 60 ° C. Using a circulating heat pump will probably require about 5 cycles for the hot water pump. And when the temperature of the water tank reaches more than 40 ℃, the heat transfer efficiency will decrease at the same time due to the decrease of the temperature difference, resulting in a drastic reduction of the heating efficiency in the later stage. The second: In the heat pump unit is equipped with a small insulation tank and a large water tank, heat pump unit first small tank filled with water, the small tank water heated to 55 ℃ and then through the circulating water pump to the large tank. As a result, the small tank increases the cost and failure probability of the equipment; both, increasing the circulating pump also adds to the cost and failure probability of the equipment. In the past on the study of circulating heat pump, most of the time, the temperature inside the water tank are maintained at 50 ℃, when the cold water into the tank, the tank temperature decreased by about 5 ℃. This time the heat pump temperature sensor driven heat pump and circulating pump start, when the temperature reaches 55 ℃, the device stops running. As a result, the daily starting and stopping times of the equipment are maintained at a fairly high frequency. As we all know, the instantaneous starting current of the compressor is large. Similarly, the high frequency start and stop of the compressor mean the decrease of the life span and the significant energy consumption increase. Circulating heating system is to make up the cold water directly to the hot water tank, leading to instability of the water tank, customers often complain. Circulating heat pump hot water unit, water tank hot water absorption refrigerant heat, the refrigerant is not fully cooled, the system is in a state of high pressure for a long time, the compressor to overcome the system pressure consumed by more energy, so that the compressor life is short: a, through Fan speed reduction to reduce endothermic; b, through the decompression device to reduce system pressure; c, put less refrigerant to reduce system pressure, unit operation efficiency is low.