[Abstract]: The variable flow of air conditioning cold water system, using a primary pump system, and a pump using frequency control, then the use of constant pressure control is not the most energy-efficient control, to achieve the greatest energy saving effect, the pump frequency control The use of variable pressure control, the system pressure changes along the pipeline characteristics curve changes. [Key words]: air conditioning, cold water system, variable frequency control of the pump, 1 cold water system, a variable flow pump frequency control. With the self-control technology and automatic control products mature, the current air-conditioning project, the application of variable flow water system has accounted for the vast majority, especially in large and medium-sized air-conditioning systems, almost 100% utilization. In the performance of chilled water unit variable flow [2], chilled water unit in the partial load of its frozen water can vary within a certain range, and has little effect on the efficiency of chillers, cold water system and the load side of the variable flow can be combined with the design , Which is used in the cold water system, a pump variable flow system, a pump directly by the frequency control is possible to give full play to the variable frequency pump excellent energy-saving effect of frequency conversion, the comprehensive energy-saving effect is significant, but the control method used is different, Its energy-saving effect is also different. Cold water system variable flow, the end of the electric two-way valve according to the room temperature control switch, causing the system flow changes, resulting in cold water supply and return manifold pressure changes, in order to chilled water pump frequency control to adapt to the system Flow changes, the system still needs to set up a water supply and return water pipe bypass valve as a backup, when the flow to the chiller minimum flow, chilled water pump lock, no longer continue to reduce the flow rate control, then start Auxiliary by-pass electric 2-way valve bypasses part of excess flow because chillers are usually more than one, as in the case of two, by halting the flow of a host has been reduced by 50% and the chance of a further reduction to 50% Not much, so auxiliary bypass electric two-way valve will not start and is generally closed. 2 variable frequency speed pump energy saving principle In the air conditioning cold water system primary pump variable flow, when the system flow from QA to QB, if the constant speed pump, its working point from A to B ', the system pressure, the system The surplus pressure head is the most, but also the least energy-saving; if the variable speed pump with constant pressure control, when the set pressure is HA (HB), the pressure sensor detects the pressure difference (HB'-HB), issued a control command, Reduce the output frequency of the inverter so that the pump's condition curve from n0 change to n1, constant pressure value to maintain HA constant, obviously lower than the constant speed pump (HB'-HB) this period of dynamic pressure loss, so than the constant speed pump Obvious energy-saving effect; however, if the variable frequency variable speed variable-pressure control of chilled water pump, the pressure changes along the pipeline characteristic curve changes, then the control device sends a control command to make the pump operating curve from n0 to n2, the actual Working point B "point, than the constant pressure control and then reduce (HB-HB") this period of dynamic pressure loss, so the most significant energy-saving effect. 3 variable frequency control pump energy saving In the above analysis, we can see that the current frequency control pump often used constant pressure control, although the control is relatively simple and easy to implement, just set a pressure value and pressure feedback signal, through Frequency control to maintain the same system pressure, which is also derived from the feed water pump frequency control of constant pressure water supply, at present there are already quite mature stereotypes in the country, manufacturers are also many, but such a constant pressure control directly Applied to the control of air conditioning and cold water systems is not appropriate, is not the most energy-efficient control methods, the above analysis shows that the most energy-efficient control is the use of transformers control, the pressure of the control system along the pipeline operating characteristics of the curve changes, the Energy-saving effect is the most significant, so the variable frequency speed control of frozen water pump control device must be programmable control chip can be achieved. Cold water system is installed, the first measured when debugging system flow changes, changes in the total pressure difference and the frequency of frozen water pump frequency relationship, a single run and parallel operation of the situation, the commissioning of all data measured induction and simulation, Actually, the approximate calculation formula of pipeline working characteristic curve is formed, and then it is stored in programmable control chip as the basis of variable frequency speed regulation of chilled water pump in operation. The principle of minimum pressure difference is preferred in operation. The average frequency, frequency conversion to chiller minimum frequency lock, chilled water pump starting from the low frequency change. In the current engineering applications, if the project uses building control system, and control of air-conditioning system included, to achieve the above transformation control is not difficult, but if the project did not use building control system, because there is no transformation Variable speed control stereotypes products, to achieve there is a certain degree of difficulty, due to procurement, and ultimately had to use constant pressure control, in fact, the current level of technological development and development, with programmable control chip control device has been very easy To achieve this, also called for the control of manufacturers for the characteristics of air-conditioning system, the development of variable-pressure control of frozen water pump variable frequency speed control of stereotypes products, can make the application of the transformer control more convenient and achieve more energy-saving effect. 4 Conclusion Air conditioning cold water system variable flow, chilled water pump using a pump frequency control, chilled water pump to achieve the largest energy-saving effect, variable frequency control of chilled water pump variable frequency control should be used, the system pressure changes along the pipeline characteristics curve changes , It is recommended that manufacturers develop the corresponding stereotypes.
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First, Sealand meter is certified by Zhejiang Institute of Metrology. To get such certificate, Sealand has to send all models to Zhejiang Institute of Metrology and all models are tested in their calibration lab. The lab is an ISO/IEC 17025:2005 standard lab approved by CNAS (China National Accreditation Service for Conformity Assessment). CNAS is a member of ILAC (International Laboratory Accreditation Cooperation).
Second, Sealand has its own calibration lab, equipped with METTLER TOLEDO scales with accuracy 0.014% and the device extended uncertainty is 0.05%. The lab is also approved by Zhejiang Institute of Metrology. This certificate will stay valid only for one year, Zhejiang Institute of Metrology will send their professor to Sealand every year to check and make sure that the lab is qualified still and then issue new certificate. During the production, each meter will be calibrated in this lab for 3 times, each time at 5 different flow rate.
Finally, Sealand also gets ISO, CE, SIL, ATEX & IECEx. Sealand is the only Chinese brand who gets ATEX & IECEx and it is from TUV SUD ( the most authoritative institute for ATEX).
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