Weak current College】 【expansion valve to showcase temperatures】.

<br> Expansion valve to showcase the temperature distribution is an experimental study on the impact of <br> Feng Jun 1, Sun case 1, Chen Yun Kum-1, 1, original Xu Yuan Xiu Ling 1, Cui Yong, Jin Yi, .2 2 Summary: on the thermal expansion valves and electronic expansion valve controlled temperature distribution within the display cases do the experiment. The results showed that the thermostatic expansion valve control, showcase the temperature in the distributions and electronic expansion valve is not much difference. In .current practice, thermostatic expansion valve basic meets General customer showcase usage requirements, there is no need to conduct large scale electronic expansion valve replacement. <br> Keywords: electronic expansion valve, thermostatic expansion valve; showcase 1 introduction with refrigeration technology continues to develop, .on the refrigerant flow control requirements are also getting higher and higher, due to thermal expansion valves of some inherent defect cannot be overcome, electronic expansion valve launched a large number of applications, and has achieved remarkable results, many scholars believe that electronic expansion valve replacement .thermostatic expansion valve is imperative. However, a lot of refrigeration products has its peculiarities, one part is the need for alternative you should consider many factors. In a display cabinet, cabinet temperature on food freezer has a bigger impact, and thus can make cabinet .temperature is improved, should become the electronic expansion valve in the showcase when used in the main factors to consider. In order to compare the thermal expansion valves and electronic expansion valve in the actual control in the showcase performance, this article on two expansion valve control .display cases made of temperature in a comparative study, and thus to the expansion valve applications have a more comprehensive understanding. 2 analysis and comparison in the refrigeration system, the expansion valve's flow regulation performance on evaporator utilization, variable load adaptive capacity is greatly affected. .Thermostatic expansion valve because of the long history of development, the technology is more mature, almost to all types of refrigeration systems. However, with the development of society as well as on energy issues of concern, fostered began to seek a new expansion valve, .energy-saving, easy maintenance, overall control becomes critical. In order to adapt to this situation, electronic expansion valve for a wide range of research and found that in some ways it is more adapted to the current refrigeration equipment control requirements. For example, .in the heat pump, due to the structure and principle, thermostatic expansion valve cannot make refrigeration and heating while running at peak performance. Moreover, due to winter and summer heat pump units of cooling capacity, individual thermostatic expansion valve cannot be in both cases effective .adjustment. And the electronic expansion valve it can meet the heat pump units for the full year of operation. In addition, for a compressor energy VFD refrigeration system, using electronic expansion valve can be very good with system-wide electronic centralized control. Visible, .if you want to increase the level of refrigeration products, electronic expansion valve is essential for the application. However, we should see the specific design of the system itself, along with some related parts of the match, in many practical situations, the advantages of .electronic expansion valves and not very good. In the display cases, the use of electronic expansion valves can indeed improve certain aspects of performance. For example, make the more uniform heat transfer coefficient, which reduces the evaporator temperature difference. But from a holistic point .of view, the use of electronic expansion valves and the benefits is not as expected. First, display cases like heat pump air conditioner refrigeration system such as evaporating temperature range is particularly large, so for now, thermostatic expansion valve has been able to meet the .control requirements. In addition, because of the frequency inverter compressor, fan and not widely used in the display cases, electronic expansion valve in the current showcase products and does not give full play to its effects. Second, electronic expansion valve General must and specific .modules with can very well play their control capacity, in order to use the electronic expansion valve and increase control module and other hardware and software that will definitely increase the cost of the system. Because the price is the number of consumers to buy goods on the .main factors taken into account, so electronic expansion valve for use if you cannot make the product's overall performance is significantly improved, there is no need to increase the product's market price that affect competitiveness. Today, due to the application of advanced technology, temperature filling .pattern package has been improved so that the thermostatic expansion valve control characteristics are a great improvement from the temperature control in the showcase, and electronic expansion valve difference is not very big. Thus the current showcase production, if the customer on system and uses no special .requirements, there is no need for comprehensive electronic expansion valve replacement. In order to compare the thermal expansion valves and electronic expansion valve of the temperature control performance, we are on a single display cases made a related test, because only from the perspective of practical .application, this experiment will only compare and refrigerated and frozen food temperature inside the Cabinet and its changes. 3 experimental facility describes test with thermostatic expansion valve is Danfoss (DANFOSS) company's external balance thermostatic expansion valve, nominal cooling capacity as 6.0kW. Electronic expansion .valve using a Danfoss ADAP-KOOL series AKV10-electronic expansion valve, nominal cooling capacity as 7.1kW. Electronic expansion valve with Danfoss AKC114A type evaporator controllers control a, Figure 1-Schematic of the controller connection. AKC114A pulsewidth, by changing the duty cycle .(one cycle off time / a cycle of time) to control the expansion valve coil power on or power-off, the control valve to open or close the time period of 6s. You can control panel on a variety of control requirements set. A .cycle valve opening and closing time depends on system load, when the system needs rapid cooling, expansion valve opening time increases, or even the entire cycle is on; when the system's cooling capacity tends to stability, expansion valve opening time relatively less. 4 experimental .results and analysis of Figure 2, Figure 3 respectively thermal expansion valves and electronic expansion valve control cabinet changes in temperature. <br> Experimental data shows that the thermostatic expansion valve control, system startup 22min, inner wind curtain outlet temperature reaches-20 ℃; .electronic expansion valve reach this temperature experienced 21min, electronic expansion valve response faster. Starting from the beginning to the cabinet temperature stable, thermostatic expansion valve experienced about 75min, Electronic expansion valve has undergone 93min, thermostatic expansion valve quickly 28min. Because this kind of electronic .expansion valve to open degree only full open and full closed two situations, compared with thermostatic expansion valves, starting phase of more prone to fluctuations, thus achieving stability in the desired time is longer. Table 1 for both cases inside temperature contrast. When the inner .air curtain outlet temperature reaches-20 ℃, thermal expansion valves control the average temperature is-10.6 ℃, electronic expansion valve for-11.4 ℃, electronic expansion valve of the air temperature difference small 0.8 ℃, which is sent to a different degree of dampness .. When cabinet temperature stabilization, thermal expansion valves and electronic expansion valve control inner wind curtain average temperature of 27 ° c, respectively - and-26.8 ℃, the difference was not significant. In thermal expansion valves control the temperature in the Cabinet, top divisions .after stabilization of the average temperature is-22.3 ¡ .æ,-media divisions for-18.5 ℃, the lower divisions as-17.3 ℃; electronic expansion valve corresponding temperature respectively-22.5 ¡ .æ, -17.8 ° c and-16.1 ℃. Visible, thermostatic expansion valve control cabinet temperature to more uniform. In addition, under the control of electronic expansion valves, the average temperature in the Cabinet as-stable after 18.8 ℃; thermostatic expansion valve .for-19.4 ℃, by contrast, closer to the design requirements. From the above analysis shows that the use of electronic expansion valves and no to showcase of temperature distribution of a significant improvement. On the contrary, the temperature reaches a stable time, Cabinet .air temperature uniformity, thermostatic expansion valve than electronic expansion valve to better. It should be noted that, as a result of this experiment is under certain conditions, it may not be extended to other conditions or other refrigeration products. 5 conclusion this article on thermal .expansion valves and electronic expansion valve to control the temperature in the next showcase Cabinet. In both cases, showcase cabinet temperature differences are not large. Therefore in the showcase practical applications, if the system or control does not have special requirements, thermostatic expansion valve is .essential to meet the requirements. It is not necessary to fully implement the alternative electronic expansion valve. Reference documents <br> [1] on Lei, Lu Zhen, fan forest. Air-cooled heat pump applications in electronic expansion valve and thermostatic expansion valve .of refrigeration technology [J]. 2001, (4): 22-24..