【School】 induced weak VAV air conditioning system design --- Power By 【China】 weak home network..

<br> Abstract: VAV terminal unit induced the advantages and design, that induced VAV terminal also apply to the office, especially in hospital wards air conditioning, the room can effectively improve air quality and improve comfort.. All-air system, can .inhibit microorganisms, bacteria breeding and reproduction of authors: Jia Jie Yan Huo Xiaoping 1 Introduction induced VAV air terminal is widely used in the Nordic VAV terminal.. It is not only energy-saving features, and because it is a full-air system, .removing condensate link, effectively prevent the breeding of microorganisms to improve the room's air quality, improving the room environment.. Induced VAV offices and hospital wards for such occasions require a higher comfort, can effectively inhibit the reproduction of bacteria, to prevent the spread of .germs and cross infection.. VAV air-conditioning induced to develop the end of the building is to improve the quality of the indoor environment is a good way.. This paper on induced to make some of VAV air conditioning system.. 2.1 2 induced .VAV terminal end of the principle of inducible induced VAV VAV terminal is through the focus of the air (primary air) into the air-conditioned room by the fan in the induction unit, induction unit is divided into various rooms in the local device (or .. end of the device).. It is from the plenum chamber, intake device (nozzle, VAV control valve) and coils (also known as the secondary coil, coil and some without) and so on.. Primary air into the induction unit .of the plenum chamber, the injection nozzle at high speed (20 ~ 30m / s).. Ejector exhaust flow due role in the induction of negative pressure inside, indoor air (ie, return air, also known as secondary air) is inhaled induction .unit, the first and second winds of the air sent by the induction unit.. Into the induction unit is usually a wind of fresh air, if necessary, can also use part of the return air, but when using the return air duct system is .more complex.. Induced VAV terminal unit is the main part of the induced air, and its role is to use a wind speed induced by the interior into the roof of the secondary air, after mixing into the interior.. There are three terminal devices .induced, one is the primary air, secondary air at the same time regulation, the largest indoor cooling load, the secondary air (wind induced) side of the valve is fully closed.. As the load decreases, opening the second valve to change the .primary air and secondary air mixture to increase the supply air temperature.. Since it with a valve opening proportional induced change, so the control difficult.. To do this using another structure, namely at a constant air volume air jacket body.. With the .indoor load decreases, and gradually turn up the second damper to improve the supply air temperature.. There is a third structure, which tops in a VAV air devices, variable air volume conditions in the induction of the indoor return air.. This structure is .the development of induced VAV mainstream, but also focuses on the object of this article.. Induction is one of the performance indicators of induction ratio n.. n is usually between 2.5 to 5, with the product mix varies.. For a certain structure .of the induction unit, in a certain range of wind n constant.. Induction unit target for some other characteristics of job stress (and nozzle speed related), rated a noise when the air flow, cooling and heating coil capacity.. Variable air volume .system induced not only has the VAV system, energy-saving features, and can be adjusted in very small range of good thermal comfort.. VAV system induced terminal units unique design allows the indoor air induction units and fan in the case of not using it .with an air conditioning mixed.. At the same time by changing the pressure of imports, import wind speed, the lower pressure loss and set the throttle in the induction port to achieve the purpose of regulating induction ratio.. 2.2 The benefits of induced VAV .air conditioning system and the comparison with the FC system 2.2.1 The advantages of cooling mode, cooling mode, the induced VAV system shows better than the other three variable air volume system features: 1) It can use low-temperature. primary air ( .not less than 9oC), allowing designers to use less air flow can achieve the same cooling load.. At the same time reduce the pipeline system and associated air handling equipment size, can provide users with more useful space.. Also expanded the " .free cooling "of the outdoor air temperature range.. 2) Without prejudice if the premise of thermal comfort will be transferred to 20% turndown, it can reduce the air flow requirements, and allows adjustable speed than conventional VAV AHU in the smaller air volume .system to work.. This is particularly applicable to low-load and no one in the case.. 3) For the other VAV systems, the minimum air supply, generally will produce a flow of air is not "dead zone." .. The induced VAV overcome this difficulty, it provides enough air to the room air in the room to fully exercise, to ensure the comfort of occupants.. 2.2.2 The advantages of reheat mode, generally, in the cooling mode, the traditional VAV .system only able to adjust the ratio adjustment to 50% to 60% to maintain indoor thermal comfort.. This indicates that the re-heating to reach maximum capacity of 50% to 60%.. One of the larger flow of heated air then is .inefficient and energy consuming.. VAV on re-heating induced only 20% of maximum capacity, it is very close to a building of minimum fresh air requirements.. Induced VAV system has another advantage is that we can recover the heat as the lighting equipment ... With the induction of primary air to warm air, it will delay reheat coil power on time, thus reducing further loss of heat energy.. 2.2.3 General characteristics of induced VAV system 1) without the need for special or auxiliary VAV diffuser .case fan, you can achieve throttling range from 20% to 100% of the adjustment.. 2) to maintain adequate air movement and thermal comfort, and the diffuser can be eliminated when the air flow in a small stream sink phenomenon.. 3) .The operating pressure is low.. 4) can be reheated in the heat recovery mode.. 5) the induction of static pressure into useful energy.. 6) can be used at a low temperature air.. 7) can be used with the .building management system compatible with the standard pressure independent VAV control system to control it.. 8) a low-noise noise standard 24 ~ 35dB (no fan noise).. 9), compact design.. 2.2.4 induced VAV system compared with .the traditional FC (1) VAV terminal induced condensation of water because there is no problem, effectively avoid the growth of bacteria; and traditional fan coil condensate will lead to the large population of bacteria,. and into the room with the air, affecting people's .health.. (2) induced VAV terminal can basically ensure that the new wind of distribution according to need, to meet 30m3 / h person; and the traditional fan coil air difficult to meet the new room, or difficult to obtain a balanced distribution of .fresh air.. (3) inducible than VAV fan coil, the air changes improved significantly.. (4) can be induced VAV centralized management; fan coil units are arranged in all the rooms, causing inconvenience to the management.. (5) .induced a large temperature difference can be used as supply air VAV, pipe size decreases, saving space.. 2.3 Performance Analysis of inducible 2.3.1 VAV VAV terminal operation induced inducible variable air volume units, as its name suggests, variable air volume units in .the case of no auxiliary fan, induced air flow within the room or the ceiling of the air. and out of them and one from the central system air mixing.. The figure is a schematic diagram of a typical shape of the unit.. Primary .air (through the air-conditioned air) into the unit (A) section.. Unique design of the damper (B), it can control a gas flow, while in the induction room (C) the entrance to produce a negative pressure. .. Negative pressure to induce air through induction port (D) and then into the induction room (C), in the induction room and a mixed air.. Mixture of air flow through the number of export (E) even blowing, the export built .-uniform grid with a uniform treatment of the air.. 2.3.2 VAV end of the performance curve induced 1) an air flow of air curve is a straight line, it reflects from 0% to 100% throttle.. This is not induced .with variable air volume unit of the curve the same (although in variable air volume conditioning unit is less than 50%, the diffuser will appear the phenomenon of cold air sinking.) Induction ratio is the inlet pressure, wind speed and the downstream pressure of .imports. loss of composite function of three variables.. Performance curves show that: the higher the inlet pressure, the lower inlet velocity, the smaller the lower the pressure loss, the greater the induction ratio.. Air supply and air flow curve is a .superposition of curves of induced air, usually much larger than the primary air.. Without disrupting the thermal comfort and does not affect the maintenance of essential household comfort of air mobility, the induced VAV air volume control unit makes the possibility of 20% was achieved ... Figure 1 Schematic <BR> 2) Temperature into the gas volume (Q3) is the primary air (Q1) and the induction of air (Q2) and.. Inlet temperature (T3) can use the induction ratio, an air .temperature (T1) and the induction air temperature (T2), calculated using the following formula: oC, for example, the maximum flow rate:,, induction ratio = 1.35; minimum flow.: induction ratio = 2.153 induced VAV system design process 3.1 .Design Standard is a maximum flow of air from the space and time required for air conditioning the temperature of the decision; minimum flow is usually based on the hours required to maintain energy consumption can be. meet the needs of the minimum fresh air.. In .general, the lower the pressure loss can be designed for the 20 ~ 60Pa.. Designers can select the desired ratio of imports induced by static pressure, to keep the intake air temperature is greater than a minimum value or meet other needs.. In order .to maintain the minimum energy consumption, it is recommended static select 150 ~ 250Pa.. VAV systems and present comparison, the inlet pressure looks a bit high.. However, we should know: an inducible import variable air volume units include the downstream 50Pa static .pressure loss, whereas the downstream pressure losses must be added to the pressure drop in to the VAV unit.. If a VAV unit with 100Pa pressure drop, loss of downstream pressure 50Pa, then it requires a minimum static pressure is 150Pa to work properly. ..3.2 induced VAV design a room available for example, if we want it to VAV air-conditioning design, according to the following steps: given parameters: 1) Design standard: Room size: 3.6 × 5.4 = 19.4m2 downstream pressure loss. ( .P3) = 40Pa an air temperature (T1) = 12 oC room air temperature (Tr) = 24 oC induction air temperature (T2) = 25 oC minimum air temperature (T3) = 15 oC per person minimum fresh air = 11 l. / .s2) cooling load: 2 × 80W / per person = 160W Lighting (10W/m2) × 19.4 m2 = 194W computer terminals, printers, etc. = 400W solar radiation (maximum), etc. = 550W of total heat load (P) .the maximum .= 1304W heat load = 67.2W/m2 design parameters: A.. An air flow rate () B.. Requires induction ratio () C.. Minimum inlet pressure () D.. The total volume of air (primary .air to take the minimum time) () E.. Induction ratio (the minimum time taken when the air) () F.. The total air temperature (the minimum time taken when the air) () the design process: A.. .An air flow rate () = cooling load () = specific gravity (=) = specific heat (enthalpy )(=)= room air temperature () = primary air temperature () B.. Requires induction ratio () when the supply air .temperature to take the minimum, the requirements of induction ratio calculated as: or: C.. Minimum inlet pressure (P1min) minimum inlet pressure depends on the induction ratio obtained by look-up table.. Induction ratio at the same time with the primary .air flow correction factor (K1) and downstream of the pressure loss of the correction factor (K3) on: For Model 125, it's dressing factor is: = 1.00 = 0.96 can be seen from the induction ratio, when. we have 125 types of .units is taken as the minimum inlet pressure 360Pa, the time of its induction ratio is 1.3.. If you choose the larger size of the unit inlet pressure will be reduced.. For example, the size is 160 units, it is the correction factor .is: 160 units for the model, the only 240Pa pressure can get the import of the induction ratio of 1.3.. D.. The total volume of air (primary air to take the minimum time) () a minimum of air flow to determine .the minimum fresh air requirement based on: we can find out from the map when the inlet pressure is 350Pa, adjust the ratio is 24.5%, the total delivery. airflow Yes Yes: E.. Induction ratio (the minimum time when the air get .()): F.. The total air temperature T3min (taking the minimum primary air) or: the figure of 100% when adjusted when the ratio value is obtained at a mean air velocity (8 ~ 10m / s) based on the derived ... By the model size (refer to table "a correction factor for air flow (K1)") and downstream pressure drop (30Pa) to decide.. Otherwise, use correction factors: the primary air flow (V1) of the .correction factor (K1) Model size V1 <values chart graph values V1> Numerical 4133167200233267300333367400516720825029233337541745850062773464154845536236927618308442552663773883994110412151325106838541025119613671538170818792050 figure lower pressure drop correction factor K11.121.081.051.031.000.980.960.940.92. (P3) correction factor (K3) P3202530354045505560K31.041.021.000.980. .960.940.920.900.89 comfortable with the new development of international standards (eg NEN, DIN, ISO, BSRIA, ASHRAE, etc.), a VAV system, nor if there is no induction unit. using a dedicated VAV diffuser, when the flow .dropped to 50% to 60% would be difficult to prevent sinking diffuser air flow phenomena, it is difficult to ensure adequate flow of room air and continuous thermal comfort.. And an inducible type of VAV unit, only 20% of the adjusted ratio of .thermal comfort to satisfy the requirements of the standard, indicating that the VAV system can be induced to save a large part of the user running costs.. 4 VAV System induced inducible form of VAV terminal that there are many with rectangular exports, with exports and .built rectangular coil in the heating and multiple re-export with a built-in heating coil.. Induced VAV terminal for office buildings, hospitals, and many other occasions, especially for hospital wards.. Its biggest advantage is that omitted this part of the .condensate, so no breeding place for bacteria, reducing the spread of bacteria in hospital wards and cross-infection.. It has a traditional air system does not have all the advantages of duct size decreases, saving space area.. The disadvantage is relatively noisy ., speed control is not easy to induce than the control difficult.. VAV terminal will be induced with the combination of automatic control, can further improve control accuracy, to achieve the desired control objectives.. 5 Conclusion In summary, induced VAV terminal because of .its many advantages, it is very worthy of a system.. VAV terminal will be induced for the office, hospital ward air-conditioning system, fan coil solve many defects, for the people's lives more comfortable living environment.. References: (1) .Zhao Rongyi and so on. Air conditioning. Beijing: China Building Industry Press, 2002 (2) Barcol-air product brochure 1996 (3) HVAC Systems and ASHARE HANDBOOK 1992..