【 Weak current College 】 air-conditioning closed water system head formula

<br> On the closed water system: <br> Σ △ h = Hf + Hd + Hm. .<br> Hf, Hd-water system frictional resistance and Pa local resistance loss. <br> Hm-Pa device resistance loss. <br> Estimation method of frozen pump lift <br> Here are talking about is a closed-type air conditioner .cooling systems of resistance, because this system is of common systems. <br> 1. water chillers resistance: provided by the Unit factory, usually 60 ~ 100kPa. <br> 2. piping resistance: including friction resistance, local resistance, friction resistance .per unit length of that group than friction depends on the technical and economical comparison. If a value greater then the pipe diameter is small, the initial investment in the province, but the energy consumption of pump operation; if the value of small and large, .on the contrary. The current design of cold water pipe than friction group should be controlled at 150 ~ 200Pa / m, diameter is large, the value can be smaller. <br> 3. air conditioning is not end device resistance: Terminal units for .types there are fan-coil units, packaged air conditioners, etc. Their resistance is based on the design of air into and out of the air conditioning coil parameters, cooling capacity, water temperature, from the factory through the coil configurations calculating available, many .of the rated operating conditions on the values in a sample of the product cannot be found. This resistance is generally 20 ~ 50kPa range. <br> 4. pressure resistance: air-conditioned room is always requires control of room temperature, in air conditioning .terminal device of water on electric regulating valve is two-way room temperature control. 2-way valve specifications by valve fully open when flow capacity and allows to choose a pressure drop. If this allows for the pressure loss value and the control of the valve .to a good performance; if value is small, the control performance is poor. Valve fully open when the pressure loss of the slip road to a percentage of the total pressure drop is called the right of the valve. Water system design requirements valve right degrees .S> 0.3, so two-way control valve allows for the pressure loss is generally not less than 40kPa. <br> According to the above, can produce a rough estimate of about 100m high high-rise building air-conditioning system pressure loss ., that is, the circulating pump head: <br> 1. water chillers resistance: 80kPa (8m water column); <br> 2. piping resistance: frozen in the engine room of the strainer, water harvesting, water separator and pipeline, .resistance to 50kPa; for transmission and distribution piping length 300m and side than friction 200Pa / m, the friction resistance for a 300 * 200 = 60000Pa = 60kPa; consider the distribution side of local resistance to the abrasion resistance of 50%, then the local .resistance to 30kPa 0.5 = 60kPa *; the total resistance system piping to 50kPa + 60kPa + 30kPa = 140kPa (14m water column); <br> 3. air conditioning terminal device resistance: combined air conditioner resistance than the fan coil resistance, so take .the former resistance to 45kPa (4.5 water column); <br> 4. the resistance of the two-way control valve: 40kPa (0.4 water column). <br> 5. Thus, the water resistance of each part and as: 80kPa .+ 140kPa + 45kPa + 40kPa = 305kPa (30.5m water column) <br> 6. pump lift: 10% safety factor, then lift h = 30.5m * 1.1 = 33.55m. <br> According to the above estimates as a result ., you can scale the basic master class with building air-conditioning system of the pressure loss value range, and in particular should prevent without calculation, too conservative, and the system pressure loss estimation, pump lift selected too large, leading to energy waste. .<br> Σ △ H refers to the system the most negative loop frictional resistance and local resistance and plus the chiller resistance and the resistance of the terminal device <br> Cooling towers of pump selection <br> I would like to ask that the cooling .water system is generally more open system, it has a height difference (also called the hydrostatic pressure) <br> This value is the lowest point of pump suction to the highest point of elevation difference, or cooling towers nozzle-to-ground height difference .<br> I personally think that the former, but still not sure <br> Hydrostatic pressure should be the pump stopped state, the still liquid cooling towers to pump or a high end equipment. <br> Pump lift = pipe frictional resistance + local .resistance + device resistance + cooling tower water distributor pressure + water distributor to set water height difference <br> Cooling tower water distributor pressure and spray pressure is not a call! <br> I personally think that the tower head is determined to be, condenser .60 to 100KPA, along with local resistance of 80 to 120PA per metre, cooling spray pressure 50KPA, plus cooling tower water lifting height, then x, K = 1.1 ~ 1.2, does not know such figured out of the lift and the actual size of .the error? <br> I think the condenser 50 to 80KPA, along the 300 + local resistance to the cooling tower 500PA per metre spray pressure 50KPA, plus cooling tower water lifting height, then x, K = 1.1 ~ 1.2, <br> .100KPA resistance of condensers, I do a design almost never seen <br> If the coefficient is laminar as 64/RE,. turbulent as 0.3164RE (- 0.25) (do not know the superscript does not display, RE-0.25 is in the .upper corner), critical of RE-2320. dynamic pressure value in 2000 to 4000PA, velocity values, generally within 2 to 3 almost. such figured out it was frictional resistance, Hd / Hf small residential building to 1 to 1.5, large skyscraper 0.5 .~ 1, distance (central cooling) 0.2 ~ 0.6. This should work out of relatively closer to it, if it is a small house, 300 or so, the design uses central cooling that results in more than 200 following £ ® is a closed .system, open type of addition of hydrostatic pressure. <br> Do not know so much with the actual gap? <br> Take the 300-500PA is considering water pipe on valveAnd fittings, and general design use along 200PA-300PA <br> .Hydrostatic pressure should be the pump stopped state, the still liquid cooling towers to pump or a high end equipment. <br> Pump lift = pipe frictional resistance + local resistance + device resistance + cooling tower water distributor pressure + water distributor to set water height .difference <br> Agree that there are coefficients 1.1 ~ 1.2 <br> Cooling towers-head calculation formula is: <br> Head = pipe frictional resistance + line local resistance + condenser side of resistance + cooling tower water lifting height (from the bottom .of the pool of cooling towers to spray with high difference * 0.0098MPa) + cooling tower water distributor nozzle spray pressure (GFRP cooling tower wind-about 0.02 --- 0.05MPa, water jet cooling tower approximately 0.08-0.15MPa) <br> .The above is taken from the national survey and design registered public equipment engineer HVAC professional exam review course materials <br> Posted in HVAC freedom Forum discussions-excessive cooling pump lift <br> Used in the cooling water system pumps, chiller placement in 2 / .f, Tower is placed in the 5th floor, cooling pump was also placed on the 5th floor. Pump running noise mega will pump outlet valve down noise immediately reduce replaced numerous bearing cannot be resolved, please boss appreciated! (empty) zr <br> .£ ® And bearing no relationship, pump lift too large so the most likely. Can the cutting blade. (Empty) hyy3721 <br> I lift selected 30 m should have '(null) zr <br>. Calculate resistance. (Empty) .hyy3721 <br> Provide water pump outlet pressure gauge. readings. (Empty) tu <br> £ ® Pump outlet pressure only 2.2KG/CM pump factory maintenance personnel that lift selected is too high in other parts of the towers and hosts on the .same floor are only 20 m selected 30 m lift never so happens the difference between the system that works well is the actual height greater lift to instead selected small only? Halo! (empty) zr <br>. Lift selected is too high, it .is estimated that on export, to set the water plate height difference, 5 2 ~, height difference, the problem raised multiple times in the Forum. WCDMA old said many times, you find out. (Empty) tu <br> He also PCT .said 50 times. in. ^ _ ^ (empty) tu <br>. "Water pump outlet pressure only 0.22 MPA" on your system in water pump flow rate significantly exceed the design requirements, piping system actually lift only 22 meters. If this .is the normal design flow, may 18 m is not finished! (empty) in WCDMA <br>. Read out the condenser and export the pressure differential, control rated flow and pressure ratings, you can calculate the actual volume, and then control the .import and export pressure pump, you can calculate the actual pump lift. (Empty) hyy3721 <br> Example: a system, cooling water pump rated lift 31m, measured 21m, evaporator pressure rating, measured 12m 5.5m, calculation of the actual lift .12.6m. (Empty) hyy3721 <br> <br> <br>.