水泵选型（Pump selection）

水泵选型（Pump selection） 水泵选型(Pump selection) The first step: determine the flow of water pump Cooling water flow rate: for the cooling water flow of the corresponding chiller, the pump flow should be added 5% to 10% margin, or calculated according to the following formula. L= (Q1+Q2) / delta tx1.163X (1.15~1.2) Among them: L is the cooling water flow rate, m3/h; Q1 is the total cooling load after multiplying the usage rate, kw; Q2 is the power consumption of the compressor in the unit, kw; T is the cooling water inlet and outlet water temperature difference, temperature, generally from 4.5 to 5. The second step: Determination of pump lift Determination of lift head of chilled water pump 1. chiller evaporator water resistance: generally 5 ~ 7mH2O; (specific value can be seen product samples) 2. end equipment (air handling unit, fan coil, etc.), surface cooler or evaporator water resistance: 1 For 4 ~ 6mH2O; (specific value can refer to product samples) 3. backwater filter resistance, generally 3 ~ 5mH2O; 4. water separator, water collector resistance: general one for 3mH2O; 5. refrigeration system pipe frictional resistance and local resistance loss, friction is friction resistance (80 ~ 120Pa/m) multiplied by the length of the pipe. The local resistance is 50%. of the resistance along the path To sum up, the head of the chilled water pump is the sum of the aforementioned resistances. Determination of the head of a cooling water pump The head is the resistance of the cooling water system + the pressure difference between the cooling tower and the water tank to the water distributor 1., select more than one pump, we should consider the flow of attenuation, generally add 5% to 10% margin 2. parallel pumps should not exceed 3 units, that is, the choice of refrigeration, the host should not be more than three units. 3. large and medium-sized projects should be equipped with cold hot water circulation pump Central air conditioning pump type selection (submerged pump) we more trusted Shanghai Hong Ya machine pump manufacturing Co., Ltd. Water selection design of central air conditioning system Abstract: the calculation of the selection of water pump is actually an estimate (many calculation formulas are in itself estimated), the calculation of points is more detailed, and the contents considered are comprehensive and accurate calculation. Including pump selection index, water pump lift simple estimation method, the practical calculation method of water pump head, pump head design, etc.. Key words: water pump selection Pump head Lift estimation Equipment resistance Cooling water Pump selection index - - The calculation of the selection of water pump is actually an estimate (many calculation formulas are in itself estimated), the calculation of points is more detailed, and the contents considered are comprehensive and accurate calculation. In particular, when the design flow in the vicinity of the rated equipment flow, the above mentioned resistance can be applied, and more often are larger than the equipment, a lot of rated flow. Similarly, the water flow rate of the water pipe is calculated and the resistance value is checked by the look-up table. The problem of excessive lift of water pump. The design of the pump head is too large, will make the rich head in exchange for increased flow, flow increases, making the pump noise increases. In particular, the increase in flow also makes the pump motor load increased, the current increased, heating increased, " Countless bearings have been replaced " It's a small matter. It's very possible to burn the motor. in addition " The pump outlet pressure is only Zero point two two MPa " What does that mean? The difference between the inlet and outlet pressure of the pump is the key. For example, pump the pump in the open system One hundred High on the top, outlet pressure, if yes 0.22MPa On this system, the water pump is placed on the ground One hundred At the top of the meter, the exit pressure is 0.32MPa The! - simple estimation method - pump lift Selection of HVAC pumps: usually choose the specific speed NS stay One hundred and thirty ~ One hundred and fifty Centrifugal water pump, the flow of water pump should be rated flow of water chiller One point one ~ One point two Double (single table fetching) One point one The two units are connected in parallel One point two . According to the estimate, you can take roughly every one One hundred M length loss for 5mH2O Pump head MH2O ): Hmax= Delta P1+ Delta P2+0.05L (1+K) Delta P1 A water pressure drop for an evaporator of a chiller. Delta P2 A hydraulic pressure drop in which the water pressure loss of the air conditioning terminal unit, which is parallel to each other, is the largest. L The most unfavorable loop. K As the ratio of the most unfavorable loop local drag and the total length of straight pipe length and equivalent, when the worst loop is longer K Value Zero point two ~ Zero point three , The worst loop is shorter K Value Zero point four ~ Zero point six - A practical estimation method - chilled water pump lift What I'm talking about here is the resistance to the cold water system of closed air conditioning, because this system is a common system. One Chiller resistance: supplied by the unit manufacturer 60~100kPa . Two The pipeline resistance: including friction resistance and local resistance, the friction resistance of unit length of friction depends on technical and economic comparison group. If the value is large, the pipe diameter is small and the initial investment is the same, but the energy consumption of the pump operation is large; otherwise, if the value is small. The friction group design of cold water pipe should be in control 150~200Pa/m Within the scope, when the diameter is larger, the value may be smaller. Three Air conditioning terminal resistance: end device type, fan coil unit, combination air conditioner, etc.. Their resistance is made according to the design of air inlet and outlet parameters of air-conditioning coil, cold, the temperature difference through the coil from the factory configured to provide the calculation, many rated value can be found on the product samples. This resistance is usually 20~50kPa Within limits. Four Control valve resistance: air conditioning room is always required to control the room temperature, through the air conditioning device at the end of the water set on the electric two way control valve is to achieve room temperature control as a means. The two way valve is selected by the flow capacity and the allowable pressure drop of the valve when it is fully open. If this allows the pressure drop to be large, the valve has good control performance; if the value is small, the control performance is poor. When the valve is fully open, the pressure drop, which is the percentage of the total pressure drop of the branch, is called valve weight. The valve weight is required in the design of the water system S>0.3 Therefore, the pressure drop of the two way regulating valve is generally not less than that of the regulating valve 40kPa . According to the above, a rough estimate can be made roughly 100m The pressure loss of the high altitude building air conditioning water system, that is, the required head of the circulating water pump: One Water chiller resistance: take 80 kPa ( 8M Water column); Two Pipeline resistance: take the resistance from the inside of the refrigerating room, the water collector, the water separator and the pipeline 50 kPa Take the length of the side line of the conveyor 300m With specific frictional resistance 200 Pa/m The frictional resistance is 300*200=60000 Pa=60 kPa For example, considering the local resistance of the transmission and distribution side as frictional resistance 50% The local resistance is 60 kPa*0.5=30 kPa The total resistance of the system line is 50, kPa+60, kPa+30, kPa=140, kPa ( 14m Water column); Three Air conditioning terminal device resistance: combined air conditioner resistance is generally greater than fan coil resistance, so take the former resistance for 45 kPa ( Four point five Water column); Four Two way control valve resistance: take 40 kPa ( Zero point four Water column). Five Thus, the resistance of each part of the water system is equal to: 80, kPa+140kPa+45, kPa+40, kPa=305, kPa ( 30.5m Water column) Six Pump head: take 10% Coefficient of safety H=30.5m*1.1=33.55m . According to the above results, the pressure loss of the air conditioning water system can basically grasp the scale of the building similar to the range of values, especially to prevent not been calculated, too conservative, and the system pressure loss estimation is too large, too large pump head selection, resulting in a waste of energy. - Design - lift pump ( One Cold and hot water piping system Open water system Hp=hf+hd+hm+hs ( 10-12 ) Closed water system Hp=hf+hd+hm ( 10-13 ) Type HF , HD - Total resistance and partial resistance loss of water system, Pa ; HM - Equipment resistance loss, Pa ; HS - Hydrostatic pressure of open water system, Pa . Hd/ HF Value of small residential buildings in 1~1.5 Between; large high-rise buildings 0.5~1 Long distance pipeline (centralized cooling) 0.2~0.6 Between。 Equipment resistance loss is shown in table 10-5 . ( Two Cooling water pipe system One Cooling water quantity of cooling tower Equipment resistance loss Device name Resistance ( KPa ) Remarks Centrifugal compressor evaporator It depends on different products condenser It depends on different products Absorption chiller evaporator 40~100 It depends on different products condenser 50~140 It depends on different products Cooling tower Different spray pressure Hot and cold water coil Water velocity at 0.8~1.5m/s About heat exchanger Fan coil unit The larger the fan coil capacity, the greater the resistance 30kPa About Automatic control valve The cooling water of cooling tower can be calculated by pressing type: W=Q/c (tw1-tw2) Kg/s ( 10-14 ) Type Q - Cooling tower exhaust heat, KW Compression chiller, refrigerating machine load One point three About 200 times; absorption chiller; refrigerator load Two point five About; C - Specific heat of water, KJ/ ( Kg oC ) at normal temperature C=4.1868 kJ/ ( Kg - oC ); Tw1-tw2 - Temperature difference between inlet and outlet of cooling tower, OC Compression chiller, take 4~5 oC Absorption chiller, go 6~9 oC . Two Pump head Required head of cooling water pump Hp=hf+hd+hm+hs+ho Type HF , HD - Overall resistance and local resistance of cooling water pipe system, MH2O ; HM - Condenser resistance, MH2O ; HS - Lift height of water in cooling tower (elevation from cooling sink to nozzle), MH2O ; Ho - Cooling tower nozzle spray pressure, MH2O Approximately equal to 5 mH2O Introduction: the so-called water pump selection calculation is actually an estimate (many calculation formula itself is estimated), the calculation of sub detailed, the content of consideration is comprehensive, that is accurate calculation. Including pump selection index, water pump lift simple estimation method, the practical calculation method of water pump head, pump head design, etc.. Key words: pump selection, pump lift, head estimation, equipment resistance, cooling water -- -- pump selection index -- -- The calculation of the selection of water pump is actually an estimate (many calculation formulas are in itself estimated), the calculation of points is more detailed, and the contents considered are comprehensive and accurate calculation. In particular, when the design flow in the vicinity of the rated equipment flow, the above mentioned resistance can be applied, and more often are larger than the equipment, a lot of rated flow. Similarly, the water flow rate of the water pipe is calculated and the resistance value is checked by the look-up table. The problem of excessive lift of water pump. The design of the pump head is too large, will make the rich head in exchange for increased flow, flow increases, making the pump noise increases. In particular, the increase in flow also makes the pump motor load increased, the current increased, heating increased, "replaced countless bearings" is a small matter, there is a great possibility, but also to burn the motor. In addition, "the water pump outlet pressure is only 0.22 MPa", can you explain what? The difference between the inlet and outlet pressure of the pump is the key. For example, the water pump in an open system is placed at the top of 100 meters high. If the outlet pressure is 0.22MPa, the system will pump the water to the top of the 100 meters high, and the outlet pressure is 0.32MPa! -- -- simple estimate method of pump head -- HVAC pump choice: usually choose specific speed ns centrifugal water pump in 130 ~ 150, the pump flow should be chiller rated flow rate of 1.1 ~ 1.2 times (single 1.1, two sets of parallel 1.2. can be roughly estimated by taking every 100 meters along the length of the loss is 5mH2O, the pump head (mH2O): Hmax= P1+ P2+0.05L (1+K) P1 water chiller evaporator for pressure drop. P2 parallel the ring in each air conditioning unit did not end pressure loss of a maximum water pressure drop. L is the most unfavorable loop. K is the ratio of the most unfavorable loop local drag and the total length of straight pipe length and equivalent, when the most unfavorable loop longer when K = 0.2 ~ 0.3, the most unfavorable loop short K value from 0.4 to 0.6 -- -- a practical method for estimating the head of a chilled water pump -- What I'm talking about here is the resistance to the cold water system of closed air conditioning, because this system is a common system. 1. water chiller resistance: provided by the unit manufacturer, usually 60~100kPa. 2. pipeline resistance: including friction resistance and local resistance, the friction resistance of unit length of friction depends on technical and economic comparison group. If the value is large, the pipe diameter is small and the initial investment is the same, but the energy consumption of the pump operation is large; otherwise, if the value is small. The friction group design of cold water pipe should be controlled in the range of 150~200Pa/m, diameter is larger, the value can be smaller. 3. air conditioning terminal device resistance: end device type, fan coil unit, combined air conditioner, etc.. Their resistance is made according to the design of air inlet and outlet parameters of air-conditioning coil, cold, the temperature difference through the coil from the factory configured to provide the calculation, many rated value can be found on the product samples. This resistance is generally within 20~50kPa. 4. control valve resistance: air conditioning room is always required to control the room temperature, through the air conditioning device at the end of the waterway set up electric two way control valve is to achieve room temperature control as a means. The two way valve is selected by the flow capacity and the allowable pressure drop of the valve when it is fully open. If this allows the pressure drop to be large, the valve has good control performance; if the value is small, the control performance is poor. When the valve is fully open, the pressure drop, which is the percentage of the total pressure drop of the branch, is called valve weight. When designing the water system, the valve weight is S>0.3, so the allowable pressure drop of the two way control valve is generally not less than 40kPa. According to the above, we can roughly estimate the pressure loss of the air conditioning water system of a high-rise building about 100m high, that is, the required head of the circulating water pump: 1. water chiller resistance: take 80 kPa (8m water column); 2. pipeline resistance: take frozen inside the room cleaner, water collector, water separator and pipe resistance is 50 kPa; the transmission and distribution side pipe length 300m and friction resistance of 200 Pa/m, while the friction resistance for 300*200=60000 Pa=60 kPa; if we consider the local resistance distribution for the side friction resistance of 50%, then the local resistance 60 kPa*0.5=30 kPa; the total resistance of the pipeline system for 50 kPa+60 kPa+30 kPa=140 kPa (14m.); 3., air conditioning terminal device resistance: composite air conditioner resistance is generally greater than fan coil resistance, so take the former resistance of 45 kPa (4.5 water column); 4., two way control valve resistance: take 40 kPa (0.4 water column). 5. then, the resistance of each part of the water system is 80 kPa+140kPa+45, kPa+40, kPa=305, kPa (30.5m water column) 6. pump lift: take the safety factor of 10%, then lift H=30.5m*1.1=33.55m. According to the above results, the pressure loss of the air conditioning water system can basically grasp the scale of the building similar to the range of values, especially to prevent not been calculated, too conservative, and the system pressure loss estimation is too large, too large pump head selection, resulting in a waste of energy. -- -- pump head design -- (1) cold and hot water piping system; Open water system Hp=hf+hd+hm+hs (10-12) Closed water system Hp=hf+hd+hm (10-13) Type HF, HD - total resistance and local resistance loss of water system, Pa; HM - equipment resistance loss, Pa; HS - hydrostatic pressure of open water systems, Pa. Hd/ HF value; small residential buildings are between 1~1.5; large high-rise buildings are between 0.5~1; long distance pipeline (centralized cooling) is between 0.2~0.6. Equipment resistance loss is shown in table 10-5. (2) cooling water pipe system; 1) cooling tower cooling water Equipment resistance loss Device name resistance (kPa) Equipment name resistance (kPa) remarks Centrifugal chiller slightly The evaporator 30~80 is determined by different products The condenser 50~80 is fixed according to different products Absorption chiller slightly The evaporator 40~100 is determined by different products The condenser 50~140 is fixed according to different products The cooling tower 20~80 varies with spray pressure The 20~50 of hot and cold water pipe coil is about 0.8~1.5m/s Heat exchanger 20~50 Fan coil unit 10~20 fan coil capacity, the greater the resistance, the maximum 30kPa or so Automatic control valve 30~50 slightly The cooling water of cooling tower can be calculated by pressing type: W=Q/c (tw1-tw2) kg/s (10-14) In the model Q, the cooling tower releases the heat, kW; the compression type refrigerator, takes the refrigerator to load about 1.3 times; the absorption chiller, to go to the refrigerator load 2. 5 or so; C - the specific heat of water, kJ/ (kg, oC), c=4.1868 kJ/ (kg. OC) at normal temperature; Tw1-tw2 - inlet and outlet water temperature difference of cooling tower; oC; compression chiller; take 4~5 oC; absorption chiller; go to 6~9 oC. 2) pump head Required head of cooling water pump Hp=hf+hd+hm+hs+ho Type HF, HD - total flow resistance and local resistance of the cooling water pipe system, mH2O; HM - condenser resistance, mH2O; HS - elevation of the water in the cooling tower (the difference from the cooling tank to the nozzle), mH2O; Ho - cooling tower nozzle, spray pressure, mH2O, approximately equal to 5 mH2O.