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Balance valve selection calculation
Balance valve in the design of choice calculation includes two parts, first of all, the choice of flow characteristics, followed by the balance valve diameter selection. 1, the choice of flow characteristics, in the heating system, the balance valve is generally installed in the trunk of the branch point, the user's hot entrance to the very heat source points, catchment and heat station flow control (including the control valve and Electric valve). When the heat load changes, often need to rely on the adjustment of the balance valve to change the flow, with changes in water temperature, so that the radiator heat capacity to adapt to the requirements of heat load. The best heat exchanger heat exchanger characteristics (including heat exchangers, radiators) to deal with the relative heat exchange and balance valve relative opening into a linear relationship, that is, to ensure that in the adjustment process, balance valve and heat exchanger synthesis Magnification factor remains unchanged, the thermal characteristics of the heat exchanger (especially the radiator) in the small flow of heat change is large; heat exchange in small flow changes. That is, when the flow rate is small, the amplification coefficient is large; when the large flow rate is large, the amplification coefficient is small; in order to keep the total amplification coefficient constant, the flow characteristics of the balance valve should be small when the flow rate is small; (1) The counterbalance valve resistance should be between 10% and 30% of the total system resistance. The counterbalance valve should be referenced to the hydraulic diagram. (2) The counterbalance valve should be given priority when selecting the counterbalance valve Larger; (3) in the choice of balance valve, in order to increase the balance valve resistance accounted for the percentage of the total system resistance, may be appropriate to choose a smaller diameter than the diameter of the pipeline balance valve. 2, the choice of balance valve caliber balance valve flow coefficient Kv formula: Where: W flow: t / h; Q flow unit: m; â–³ P pressure unit: Pa; Ï water density: g / cm. In the general heating system balance valve before and after the pressure drop between 3KPa (end users) to 300KPa (near end users), through the balance valve manufacturers to provide different diameter flow coefficient Kv 3KPa with the most adverse pressure drop, â–³ P into the formula to calculate the minimum balance of the caliber valve can flow (when fully open) if the value is equal to greater than the design flow, the caliber balance valve selection. 3, experience selection than the diameter of the pipeline 1-2. In order to improve the balance valve adjustment accuracy, save investment, the general requirements of the design of the selected valve opening in between 60 to 90%. Recommendation: Select the valve at Kv = 75% opening For self-operated flow control valves: The selected valve flow rate is typically 105% of the design flow to accommodate a ± 5% valve error. Check the system's maximum and minimum pressure difference is not within the pressure control valve. Usually self-acting flow control valve and pipe size equal. For self-operated differential pressure control valve: the general requirements of the selected valve flow in the range of self-operated pressure control valve, to ensure that the minimum self-starting differential pressure control valve on the differential pressure on it. For the current limiting check valve: In the system design and construction of the pump operation must be by adjusting the pump outlet valve, let it work in the rated range. In most water systems, circulating pumps and tanks are mostly on one level. The actual lift of circulating pumps in use is only the flow resistance of the circulating pipe and the water circulating part of the pump. Generally less than the rated head of the pump, pump curve can be seen from this situation the pump will be in over-flow condition, so that the pump and the motor overload. Excessive brushing of water circulation in the circulating pipe and the pump not only consumes large power but also affects the life of the circulating pipe and the pump. In this way, we install a pressure-limiting check valve at the outlet of the pump to ensure the pump operates in an efficient area. That is safe and economical. Central air-conditioning cold source, whether chilled water or cooling water system commonly used multiple pumps in parallel. In actual operation, most of the time for part load operation, and sometimes only need to open a water pump. At this time the system greatly reduced friction, rising water often lead to pump motor overload. Light trip, heavy burn the motor, affecting the normal operation of the refrigeration system. For example: When two pumps are operated in parallel, if one pump is stopped, the other will exceed 50% of the total flow, sometimes up to 80%. Therefore, it is recommended that the pump be equipped with a flow restriction device at the outlet of each pump when designing a parallel pump. The flow control valve is usually used to stabilize the flow rate automatically. The supermarket to provide current limit check valve, with limited current + check function. And to meet the needs of a single pump operation. Recommended for everyone to use. General selection and pump the same caliber, but this valve is adjustable, with a non-return function. Balance valve in the design of choice calculation includes two parts, first of all, the choice of flow characteristics, followed by the balance valve diameter selection. 1, the choice of flow characteristics, in the heating system, the balance valve is generally installed in the trunk of the branch point, the user's hot entrance to the very heat source points, catchment and heat station flow control (including the control valve and Electric valve). When the heat load changes, often need to rely on the adjustment of the balance valve to change the flow, with changes in water temperature, so that the radiator heat capacity to adapt to the requirements of heat load. The best heat exchanger heat exchanger characteristics (including heat exchangers, radiators) to deal with the relative heat exchange and balance valve relative opening into a linear relationship, that is, to ensure that in the adjustment process, balance valve and heat exchanger synthesis Magnification factor remains unchanged, the thermal characteristics of the heat exchanger (especially the radiator) in the small flow of heat change is large; heat exchange in small flow changes. That is, when the flow rate is small, the amplification coefficient is large; when the large flow rate is large, the amplification coefficient is small; in order to keep the total amplification coefficient constant, the flow characteristics of the balance valve should be small when the flow rate is small; (1) The counterbalance valve resistance should be between 10% and 30% of the total system resistance. The counterbalance valve should be referenced to the hydraulic diagram. (2) The counterbalance valve should be given priority when selecting the counterbalance valve Larger; (3) in the choice of balance valve, in order to increase the balance valve resistance accounted for the percentage of the total system resistance, may be appropriate to choose a smaller diameter than the diameter of the pipeline balance valve. 2, the choice of balance valve caliber balance valve flow coefficient Kv formula: Where: W flow: t / h; Q flow unit: m; â–³ P pressure unit: Pa; Ï water density: g / cm. In the general heating system balance valve before and after the pressure drop between 3KPa (end users) to 300KPa (near end users), through the balance valve manufacturers to provide different diameter flow coefficient Kv 3KPa with the most adverse pressure drop, â–³ P into the formula to calculate the minimum balance of the caliber valve can flow (when fully open) if the value is equal to greater than the design flow, the caliber balance valve selection. 3, experience selection than the diameter of the pipeline 1-2. In order to improve the balance valve adjustment accuracy, save investment, the general requirements of the design of the selected valve opening in between 60 to 90%. Recommendation: Select the valve at Kv = 75% opening For self-operated flow control valves: The selected valve flow rate is typically 105% of the design flow to accommodate a ± 5% valve error. Check the system's maximum and minimum pressure difference is not within the pressure control valve. Usually self-acting flow control valve and pipe size equal. For self-operated differential pressure control valve: the general requirements of the selected valve flow in the range of self-operated pressure control valve, to ensure that the minimum self-starting differential pressure control valve on the differential pressure on it. For the current limiting check valve: In the system design and construction of the pump operation must be by adjusting the pump outlet valve, let it work in the rated range. In most water systems, circulating pumps and tanks are mostly on one level. The actual lift of circulating pumps in use is only the flow resistance of the circulating pipe and the water circulating part of the pump. Generally less than the rated head of the pump, pump curve can be seen from this situation the pump will be in over-flow condition, so that the pump and the motor overload. Excessive brushing of water circulation in the circulating pipe and the pump not only consumes large power but also affects the life of the circulating pipe and the pump. In this way, we install a pressure-limiting check valve at the outlet of the pump to ensure the pump operates in an efficient area. That is safe and economical. Central air-conditioning cold source, whether chilled water or cooling water system commonly used multiple pumps in parallel. In actual operation, most of the time for part load operation, and sometimes only need to open a water pump. At this time the system greatly reduced friction, rising water often lead to pump motor overload. Light trip, heavy burn the motor, affecting the normal operation of the refrigeration system. For example: When two pumps are operated in parallel, if one pump is stopped, the other will exceed 50% of the total flow, sometimes up to 80%. Therefore, it is recommended that the pump be equipped with a flow restriction device at the outlet of each pump when designing a parallel pump. The flow control valve is usually used to stabilize the flow rate automatically. The supermarket to provide current limit check valve, with limited current + check function. And to meet the needs of a single pump operation. Recommended for everyone to use. General selection and pump the same caliber, but this valve is adjustable, with a non-return function.