Brief introduction: According to the simulation analysis of a pump variable flow water system, the relationship between the energy saving rate and the partial load ratio of the pump under variable flow conditions and the power consumption of the water pump relative to the chiller is obtained. The influence of variable flow on the chiller cooling performance , And gives the deviation caused by this factor in the analysis of variable flow energy saving of primary pumping system. It is pointed out that it is very important to study and master the cooling performance under the variable flow rate of chiller . An analysis of some of the common problems that have emerged in the engineering process is made. Keywords: primary pump system, variable flow, water system, energy saving 0 Introduction Air conditioning chilled water and cooling water are often run in large flow, small temperature difference. According to the Japanese experience, VWV is tied with VAV and is an energy-saving measure in air conditioners after heat exchange technology. With the development of power electronic technology and the continuous improvement of price / performance ratio of inverters in recent years, the application of AC motor variable frequency speed regulation technology is more and more widely used. Therefore, the study on variable pump system of water flow has received some attention. However, There are also many qualitative conclusions, quantitative research and calculation methods, and poor operability, thus affecting their widespread use in practice. Although the variable flow operation of chilled water and cooling water is beneficial to the energy-saving operation of chilled water pumps and cooling water pumps, the variable-flow operation may have an impact on the chiller performance, and the chiller efficiency may decrease to a certain degree . Therefore, to ensure energy-saving operation under the preconditions of chiller safety, there is a certain limit to the variation of chilled water flow and cooling water flow, and a certain matching relationship must be met. Due to the fact that manufacturers generally do not provide complete data on the chilled water chiller cooling capacity and input power as chilled water flow rate and chilled water flow rate changes under different chilled water outlet temperatures and cooling water inlet temperatures, Of the research and design has been affected to some extent; in turn, due to less quantitative research, but also makes the manufacturers have no incentive to test the relevant data. I believe a further study of variable flow water pump system for the study of improving the energy efficiency of chillers under partial load conditions and variable flow conditions will promote the promotion of energy-saving technologies to form air-conditioning water systems and refrigeration Host energy-saving research and application of the benign interaction. Effect of water-side variable flow on the chiller performance In traditional air-conditioning water system design, chilled water through the chiller and cooling water flow remained unchanged. It is considered that only by maintaining a constant flow rate, the heat exchange effect of the coil can be ensured. When the flow rate decreases, a laminar flow state may occur on the surface of the heat exchange coil to reduce the heat exchange effect; meanwhile, when the flow rate is too small, the evaporator may freeze Danger, when the flow rate is less than a certain value, if the water contains corrosive substances, will cause corrosion of the coil. With the development of control technology, the chiller control system is getting more and more advanced. Currently, different types of chillers can achieve automatic cooling capacity adjustment. The improvement of the energy regulation function of the chiller makes it possible to design variable flow on the water side, and at the same time it highlights that the pump should be changed at the same time and should be changed continually. In fact, at present, most chillers allow evaporator flow to vary within 50% to 100% of the nominal flow rate. When the evaporator with variable flow operation, the flow changes with the user load changes, when the user load becomes smaller, the evaporator chilled water flow becomes smaller, the chiller control system based on the actual cooling capacity to reduce the refrigerant flow Resulting in the refrigerant flow velocity in the evaporator coil deviating from the optimum flow rate value and the overall performance of the chiller refrigeration system is reduced. The measure of whether the variable-flow evaporator can save energy or not is not only the energy-saving of chilled water pump, but also the energy loss caused by the loss of COP value of chiller due to variable flow operation of evaporator, and then consider the load time frequency of variable flow operation degree. Due to advances in control technology, the control system ensures that the compressor is always operating in a high-efficiency zone, so that the performance of the chiller evaporator does not decrease much at variable flow rates. The influence of variable flow of chiller evaporator on its refrigeration performance is related to the type of compressor and the variable flow of refrigerant. In literature 3, from the thermodynamic point of view, it is analyzed that the reduction of COP of the chiller does not exceed 10%, even if the flow of chilled water is reduced to 60%. However, in order to ensure the heat exchange in the condenser, the condensing temperature must be higher than the outlet temperature of the cooling water, and the condensing temperature and the cooling water outlet temperature Also require a lower limit. Therefore, in order to increase the temperature difference between the inlet and outlet of the cooling water, it is necessary to increase the outlet temperature of the cooling water (usually, the inlet temperature of the cooling water is basically a fixed value), which in turn causes an increase of the condensing temperature and reduces the COP value of the chiller. Compared with the variable flow of the evaporator, the variable flow of the condenser affects the condensing temperature greatly, so the COP of the chiller is greatly changed. When installing the inverter to the cooling water pump, the variable flow of the cooling water should be analyzed in detail. The impact of performance, determine the feasibility of the program. 2 primary pump variable flow energy-saving simulation analysis Now under partial load conditions, variable flow and constant flow of two cases of system (chiller and pump) energy consumption are compared, set the flow rate chiller and pump input power were And, the case of variable flow and for the system composed of chillers and pumps, pump variable flow rate of energy saving rate (1) variable flow and constant flow in both cases the cooling capacity should be equal (), therefore, two (2) Therefore, the energy-saving rate is (3) Under partial load conditions, due to the change of ambient temperature and working conditions, the input power of chiller unit is related to the nominal energy The input power varies greatly, and the relationship is more complicated. However, although the EER changes, the change range is small, generally less than 15% [4]. Let EER change linearly with the partial load ratio η (= Q / Q0) (4) where EER0 is the energy efficiency ratio under nominal conditions, and the coefficient to be determined is related to the partial load ratio and model. If partial load is not considered Energy efficiency changes, then take. According to the definition of energy efficiency ratio, (5) From (4) and (5), the input power of chiller at partial load can be expressed by the input power and partial load ratio η under nominal conditions: Substituting equation (6) into equation (3), we obtain (7) For a closed system, the pump equivalence curve coincides with the pipeline characteristic curve and complies with the similar law in a certain speed range. (8) And respectively for the case of constant flow and variable flow of water flow. Under nominal conditions, (9) is the temperature difference under nominal conditions, and if isothermal control is used, then (10) Therefore, (11) Substituting (8) and (12) The last item in the above equation is due to the effect of variable flow operation on chiller performance. Under variable flow conditions, the energy efficiency of chillers will decrease slightly compared with the case of constant flow, and the experimental data are few in this area. In order to facilitate the theoretical analysis of the relationship between the energy saving and the flow rate change under the condition of once-variable pump flow, the following two cases are simulated respectively: When the flow rate becomes 60% of the rated flow rate, the EER of the chiller unit becomes 5 % And 10%, and EER and the relative flow rate is linear. Here for convenience, may wish to call the "5% impact curve" and "10% impact curve", shown in Figure 1. For the "5% impact curve" and "10% impact curve", respectively
PCR Plates, 96 Well PCR Plates, and 348 well plates are disposable consumables in the laboratory. They are widely used in genetics, biochemistry, immunology, medicine and other fields. They are not only used in basic research such as gene isolation, cloning and nucleic acid sequence analysis, but also Diagnosis of disease or any place where there is DNA or RNA.
The new line of white PCR products is designed specifically to optimize results when performing quantitative Real Time PCR (qPCR). The new 96 Well PCR plates are free of DNA, DNase, RNase, and other PCR inhibitors. 96 Well PCR plates have thin, uniform walls to ensure consistent, precise thermal transfer and excellent results.
96-Well PCR Plate,96 Well PCR Plate,96 Well PCR Plate Volume,96 Well Skirted PCR Plates,96 Well Plate Sealing Film
Yong Yue Medical Technology(Kunshan) Co.,Ltd , https://www.yongyuepcrtube.com