In recent years, heat pump water heater market is growing rapidly. For an emerging product, scientific, reasonable technical standards can provide a strong impetus for product development and industry development; On the contrary, the defects in the technical standards may be a negative impact on the development of the industry as a whole. This article will list some of the problems I found the current standards of the heat pump water heater.
Inlet air temperature rated to run
GB/T23137-2008 "Household and similar heat pump china solar water heater rated 20 ° C air heat pump water heater to run the inlet air temperature. Temperature than recommended by the International Electrotechnical Commission (IEC), inlet air temperature of 5 ℃ higher than the Japan Refrigeration Industry Association (JRA) standard provisions of the inlet air temperature 4 ℃. However, this seemingly small difference has a profound impact.
The operating parameters under nominal operating conditions is representative of product performance indicators, for the consideration of market competition, manufacturers in the design as far as possible under the rated operating conditions to maintain a higher evaporation temperature, in order to improve the capacity and efficiency of the heating. However, the existing air conditioning compressors, condensing temperature upper limit is generally 65 ℃, usually in the hot water temperature reaches 55 ℃, the condensing temperature is already close to the upper range. Taking into account the performance parameters of the distribution of certain discrete and the condenser of technical and economic factors, the heat pump manufacturing enterprises is difficult to take similar measures to retain the temperature margin in the air conditioning design, to ensure product reliability. Therefore, the manufacturing enterprises of the heat pump water heater uses a variety of solutions, such as the use of higher operating temperature of the pressure switch the compressor in the short term than the upper limit of condensing temperature operation; take a higher condensing temperature upper limit T3 climate type compression machine, allowing the condensing temperature up to 70 ℃,. One of the most striking is the development of a dedicated compressor for heat pump water heater.
However, due to air heat pump water heating capacity by the inlet air temperature influence the use of the residential places, when the inlet air temperature is low, there will be enough hot water. Under normal circumstances, the inlet air temperature reaches 15 ℃, the heating capacity of the air heat pump water heater can achieve a higher level, will not be enough hot water. If inlet air temperature of 15 ℃ rated running, anti-over-temperature protection for heat pump water heater in the inlet air temperature exceeds 15 ° C will play a role in the usual measures to reduce the evaporator air flow, reduce evaporation temperature, thus reducing system heat load, which makes the condensing temperature is restricted. This is a simple and effective measures to prevent system over-temperature run. Therefore, I believe, for the heat pump water heater, the condensing temperature upper limit equal to the heat pump system requirements for 65 ° C, conventional air conditioning compressor is sufficient.
I can not determine, in GB/T23137-2008 during the preparation of, the drafters of the full demonstration of the inlet air temperature of the heat pump water heater rated to run in the over-temperature protection, and perhaps in other areas have more reason to support the standard setting the inlet air temperature of 20 ℃. Stable and reliable operation of the compressor at a higher water temperature is an important topic of the heat pump water heater industry in recent years. It is puzzling that, in most cases, manufacturers are more willing to adopt the solution of high condensing temperature, including the use of the high price of R417A refrigerant; and even regardless of the limitations of the CCC certification requirements and standards for self-deployment of the mixed refrigerant. In fact, as long as the revision of the standard, rated to 15 ° C inlet air temperature as the air heat pump operating parameters, you can solve the existing problems.
The embarrassment of R134a refrigerant
GB/T23137-2008 provided for higher energy efficiency indicators, the use of R134a refrigerant system is often difficult to meet the standards. Therefore, to use R134a refrigerant heat pump water heater is almost extinct in the domestic market, but in Europe, North America and Australia, air heat pump non pressure solar water heater is still widely used refrigerant R134a.
R22 refrigerant has stopped in these areas, such as R407C, R410A and R417A) compared to other commonly used refrigerants (R134a refrigerant in the ozone loss potential (ODP) and greenhouse potential (GWP) has advantage.
When running in high condensing temperature of R134a compressor discharge temperature is low; at higher water temperature, R134a compressor can still maintain the stability of operation and reliability. R134a system is the most obvious drawback is that the thermal efficiency of less than similar systems using R407C, R410A, R417A. In addition, part of R134a systems use the high back pressure piston compressor range significantly larger than the existing rolling-piston compressors, better able to cope with a wide operating range requirements, the performance with some newly developed or under development roughly the same heat pump water heater for rolling rotor compressor.
To sum up, of R134a system of technical and economic as much as R22, R407C, R410A, R417A system. I believe that, due to the higher coefficient of performance indicators will be R134a exclude outside of the domestic heat pump water heater market strategy is not appropriate.