Copeland Special Compressor for Air Energy Water Heater and Its Application

A heat pump is a device that utilizes low-grade heat energy. The use of heat pumps to produce hot water can greatly reduce the consumption of primary energy and the CO caused by burning fossil fuels. Emissions. In China, the application and promotion of heat pump systems has entered a rapid growth track.

1. Introduction

With the rapid development of China's economy and the increasing improvement of people's living standards, domestic hot water and air conditioning in public buildings and residential buildings have become common demands. In developed countries, the energy consumption of HVAC and heat pump systems can account for 25~6-30% of the total energy consumption of society. In today's increasingly tense international energy situation, energy conservation and emission reduction have attracted more and more attention from countries all over the world. A heat pump is a device that utilizes low-grade heat energy. The use of heat pumps to produce hot water can greatly reduce the consumption of primary energy and the CO caused by burning fossil fuels. Emissions. In China, the application and promotion of heat pump systems has entered a rapid growth track.

Traditional water heaters use primary energy sources such as fuel oil, natural gas, and oil-to-gas to directly burn or use electric heating to produce hot water, and their thermal efficiency is not greater than 1, and the direct combustion heating method will also produce harmful pollutants, causing environmental and even Negative impact on security and other aspects. Air energy water heaters are considered to be a green alternative to traditional water heaters. It uses a vapor compression refrigeration cycle to reuse low-quality heat sources from the surrounding environment, such as air, soil or water and other renewable energy sources. It has the advantages of high thermal efficiency and no environmental pollution to the use area. Air source heat pump water heaters are easy to use and install, and their products and technologies have been greatly promoted in China in recent years. The discussion in this article is limited to air source heat pump water heaters. The thermal efficiency of heat pump water heaters can be as high as 3-4 (W/W). It can be found that the heat pump water heater has the highest thermal efficiency and the lowest operating cost. Compared with traditional water heaters, the savings in operating costs can bring a huge return on investment, which is one of the main reasons for the rapid growth of the heat pump water heater market.

2. Technical limitations of air-conditioning compressors in heat pump water heater applications

The system principles of the heat pump water heater and the air conditioner are the same, and most of the components used are the same or similar, but the operating characteristics of the two are very different:

First of all, air conditioners generally only operate in summer or winter/summer, and have relatively short operating hours; heat pump water heaters need to operate throughout the year and have longer operating hours. And GB21362-2008 "Commercial or industrial heat pump water heaters for similar purposes" and GBT23137-2008 "Household and similar heat pump water heaters" stipulate the outlet water temperature at 55℃. When the water is heated to 55°C or above, the condensing temperature will reach about 60°C or even higher, so the compressor is operating at high condensing pressure throughout the year.

In winter, the evaporating side of the heat pump air conditioner is outdoors, and the evaporating temperature decreases as the ambient temperature decreases. The condensing side is indoors. The indoor temperature is about 200C, and the condensing temperature is low; the working conditions of the evaporating side of the heat pump water heater are similar to that of the air conditioner. But on the cold side, since the water temperature is about 550C, the condensation temperature is high. The compressor is in a high compression ratio and high load operating condition in winter.

In summer, the evaporating side of the air conditioner is indoors, the evaporating temperature is usually below 15°C, and the condensing temperature is higher, but generally lower than 55°C. The evaporation side of the heat pump water heater is outdoors. When the ambient temperature is 43°C, the evaporation temperature will reach about 20°C, the evaporation temperature is high, the refrigerant flow rate is large, and the condensation temperature on the condensation side remains high due to the 55°C water temperature, and the compressor is in summer High load operating conditions.

Third, the improvement plan of air-conditioning compressor in the application of heat pump water heater

The above analysis and experiments have proved that the direct use of ordinary air-conditioning compressors in heat pump water heaters will cause serious reliability problems. Regarding this problem, we have learned that some manufacturers or engineering companies of heat pump water heaters using ordinary air-conditioning compressors have made improvements in the following two solutions:

Option 1: Ordinary air-conditioning compressor + auxiliary electric heating. Use ordinary air-conditioning compressor heat pump operation to heat water at 15°C to 45°C, and then use auxiliary electric heating to heat water at 45°C to 55°C. This solution reduces the discharge pressure by lowering the temperature of the outlet water heated by the heat pump, which takes care of the operating requirements of ordinary air-conditioning compressors. However, due to the use of electric heating, the energy efficiency ratio of the entire hot water heating process is low. The specific value depends on the proportion of electric heating in the heating volume, which is difficult to meet the requirements of national standards.

Option 2: "Mixed" refrigerant adopts self-configured refrigerant to reduce exhaust pressure and temperature. Since "mixed" refrigerants are rarely recognized by compressor manufacturers for performance and reliability, there are still many drawbacks: the stability of the composition control of "mixed" refrigerants is difficult to guarantee, resulting in unstable performance; "mixed" The thermodynamic performance of the refrigerant is not completely matched with the compressor, and the force of the components in the compressor has not been checked, which may exceed the design limit; the compatibility of the "mixed" refrigerant and the compressor material has not been confirmed, and the long-term reliability cannot be Guarantee.

In summary, we believe that ordinary air-conditioning compressors have technical problems that are difficult to overcome in the application of heat pump water heaters, and special compressors need to be developed in accordance with the application characteristics and requirements of heat pump water heaters.

Fourth, the application of compressor

The ideal compressor suitable for heat pump water heater applications in the Chinese market is directly related to the use effect, and users are first concerned about the satisfaction of the water temperature of the heat pump water heater. Both GB21362-2008 and GBT23137-2008 stipulate the outlet water temperature at 55℃. If further subdivided according to different use occasions, you can also find the difference in the temperature requirements of the outlet water.

For example, the temperature of water used for swimming pools and floor heating is usually no higher than 45°C: for domestic hot water, my country requires a water temperature of 55°C; the water temperature for heating needs to be higher, at least 600°C. Therefore, an ideal heat pump water heater compressor must be able to provide hot water above 55°C or even 60°C, and the corresponding condensation temperature must reach 60-65°C.

The most critical factor that affects the popularization and use of heat pump water heaters is the ambient temperature. Whether or not it can provide hot water in the cold winter is a key issue of concern. my country has a vast territory and the north-south climate is very different. In order to promote the use of heat pump water heaters to the vast area south of the Great Wall of my country, covering about 90% of the country’s population, the ideal heat pump water heater needs to be in the region with the lowest temperature of -20℃ in winter. Stable and reliable work.

Combining the above two points, an ideal compressor for heat pump water heaters suitable for the Chinese market can be drawn. The ideal heat pump water heater compressor can work in a cold environment with a minimum of about -20'C, and ensure that it can provide hot water above 55°C or even 60°C in winter.

Five, application prospects

According to the latest report issued by the International Energy Agency in 2007, China produces 22% of the world’s CO every year.

CO. It is emitted when fossil fuels are burned, and it is the main greenhouse gas that causes global warming.

Compared with traditional heating devices that directly burn fossil fuels and directly use electrical energy, heat pump water heaters can increase energy efficiency by 3-4 times, which means that the fossil fuel required for combustion is reduced to 1/4-1/3.

Therefore, the widespread promotion and application of heat pump water heaters has been regarded as a far-reaching progress in environmental protection.

In addition, my country’s energy shortages, reducing the waste of resources is urgent. How to achieve the healthy development of my country’s economy and society, energy conservation is the top priority. The government has paid more and more attention to the promotion of energy-saving equipment. Therefore, heat pump water heaters will surely receive more attention from all walks of life. s concern.

Compared with the huge water heater market today, the market share of heat pump water heaters is still very small, so the potential is huge, and it will be a new development direction for the water heater market in the future.

The ZWKS heat pump water heater special compressor combined with economizer cycle system design is a breakthrough in the existing heat pump water heater technology. It solves the reliability problem of high exhaust temperature during low-temperature hot water production. At the same time, it has excellent operating efficiency, making the heat pump The application of water heaters can be extended to the region with the lowest winter temperature of -200C in the country, covering about 90% of the country's population, with significant social and economic benefits.

Six, conclusion

The use of heat pump water heaters is superior to traditional gas water heaters, electric water heaters, etc. in terms of energy saving, environmental protection, and safety. However, the application of ordinary heat pump water heaters is limited by ambient temperature and outlet water temperature.

Emerson ZWKS scroll compressor combined with economizer cycle design provides a successful solution for this. This solution can significantly improve the working efficiency of the heat pump water heater system, solve the reliability problem of low temperature heating, and expand the operating range of the heat pump water heater. This technology adapts to the requirements of the use of heat pump water heaters in China, and has a positive and profound impact on the widespread use of heat pump water heaters in China, improving energy efficiency and reducing carbon emissions.