What is the difference between a direct heat pump and a circulating heat pump
Direct heating method:
Simple understanding is from the outside of the cold water into the heat pump unit is 60 ℃ hot water, and the device does not have a small water tank. As there is no circulating water pump between the water tank and the equipment, the opening and stopping of the equipment is completely controlled according to the level controller of the tank.
Direct thermal advantage is reflected in the following aspects:
Do not need to cycle water pump, reduce energy consumption and failure probability.
After the boot to get a steady stream of hot water around 60 ℃, do not need to wait, replenishment speed faster than the cycle, the customer encountered a large amount of the situation, the safety factor higher.
Without any auxiliary heating equipment, the water temperature can reach 65 ℃.
The internal condensing system of the equipment operates below 20 kg of pressure, reducing the high pressure of the system, allowing the compressor to operate at light load and prolong the life of the compressor.
Direct heating equipment is directly hot water to the hot water tank, even if the peak water consumption, the customer water temperature is not affected. The insulation tank is reduced by 30%. As a result of direct hot water, even if the user to run out of the water tank all the water tank, the water inside the tank are maintained at about 60 ℃, so you can use 100%. Recycled heating due to fill the cold water, when encountered a lot of water, the tank temperature dropped significantly, the tank temperature has been lower than 40 ℃. In order to ensure that the user requirements, often the solution is to increase the tank volume.
Direct heat pump hot water unit, low temperature tap water directly absorb the heat of high temperature refrigerant, so that the refrigerant is fully cooled, the system pressure to reduce the pressure, the compressor to overcome the system pressure consumption of less power, thereby extending the life of the compressor, unit operating efficiency high.
Circulation heating method, summed up in two ways:
The first : First, all the water tank filled with cold water, through the circulating water pump to the water tank into the heat pump host heat. In general, each cycle can raise the water temperature by about 10 ℃. For example, we now want to heat the temperature of 20 ℃ to 60℃, the use of circulating heat pump is about the need for hot water pump after about 5 times the cycle. And when the temperature of the tank reaches 40℃ or more, the heat transfer efficiency per unit time is reduced due to the decrease in the temperature difference, resulting in a significant reduction in the heating efficiency at a later stage.
The second: the heat pump unit in the assembly of a small insulation tank and a large water tank, the heat pump unit first filled with water tank, the small water tank heated to 55℃ and then through the circulating water pump to the hot water to a large water tank. One, the small water tank increases the cost of the equipment and the probability of failure; both, the increase in circulating water pump is equal to increase the cost of equipment and failure probability.
In the past, the study of circulating heat pump, most of the time, the water inside the tank are maintained at 50℃, when the cold water into the water tank, the water tank temperature reduction rate of about 5℃. This time the heat pump temperature sensor to drive the heat pump and circulating pump start, when the temperature reaches 55℃, the device stops running. As a result, the daily start and stop times of the equipment are maintained at a very high frequency. As we all know, the compressor starts at a moment when the current is large. The same high frequency start and stop of the compressor means a significant reduction in life and energy consumption increase.
Recycling heating system is a direct charge of cold water to the hot water tank, resulting in instability of the tank temperature, customers often complain.
Circulating heat pump hot water unit, water tank high temperature hot water to absorb 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 to consume more power, so that the compressor life is short:
A. Through the fan down to reduce endothermic;
B. Reduce the system pressure through the decompression device;
C. Put less refrigerant to reduce system pressure, the unit operating efficiency is low.