Weak current College】 【VAV and VRV systems principle and characteristics.

<br> Vav (VariableAirVolume) air conditioning system is a means to change the regulation of indoor air to warm moist air conditioning system level. Delta moderation company is the world's first design and build integration (ie set abstinence, implementing agencies and Velocity sensor in .one) of VAV control products manufacturer of BA. <br> VAV system originated in the 1960s Western powers, since the 1980s in countries such as Japan taisi, was suffering from rapid development, the most important reason is the enormous VAV system of energy- .wind. Top end ten years of universal access and development, VAV system has occupied the European, American and Japanese central air conditioning systems for approximately 30% market share, and in the world more and more countries are suffering from application. Step into the 1990 .'s, the admission of the VAV technology multistoried buildings and tall building has reaches 95%. <br> VAV system consists of air handling units, air supply / exhaust / ventilation / air pipe, VAV boxes, room thermostat, etc, this in .VAV box is the most important sector of the system. <br> A and VAV system (VAV) upwind <br> VAV system separate from other air play potential of mainly in the following areas: <br> 1. energy efficiency <br> .Because the air conditioning system in the year large sectors of the time is running under load in sector, VAV system air supply through changes to its cure at room temperature, it can significantly reduce the air blower power dissipation. According to the simulation calculation, when .the air flow reduction to 80%, the fan will reduce energy consumption to 51%; when the air flow reduction to 50% reduction of fan energy consumption to 15% will be. Annual air-conditioning load rate is 60%, VAV system ( .variable hydrostatic abstinence) can save fan power dissipation of 78%. <br> Second, the outdoor air for cooling source <br> --- Because of VAV system is a full air system in the transitional season can be a large number of accepted .as natural cooling source for fresh air, the relative air blower plate tube system, capable of drastically reducing the energy consumption of refrigerators, can also improve indoor air quality. <br> Three, non-condensing water annoyance <br> VAV system is a .full air system, cooling water pipe is not the end of the ceiling space on top, to stop the fan coil system of galling of condensation water leakage and contamination suspended ceiling. <br> IV. system with good illustrations of <br> Modern architectural .projects often require second decoration held, to accepted with VAV-box installation of VAV system air supply pipe and hose connections, air to air location can change a room separate from the change, or willfully according to the needs of the appropriate increased air outlet. .And accepted for air system or fan-coil system of building construction, no matter what the small local transformation are obviously suffering from very hard. <br> 5, system, low noise <br> Fan-coil system noise, and the scene of .VAV system noise is mainly concentrated in the engine room, the client is less noise. <br> Six, will not happen too cold or too hot <br> With VAV box of VAV system and, in General, air system, more effective regulation .of the temperature of the local area, making a reality of the independent control of temperature, stop in the local area which had a cold or hot. <br> 7, higher degree of intelligent building <br> Accepted the DDC numbers controlled VAV system .become facts about machine networking, access to building automation systems, thereby improving the intelligent building. <br> VIII. reduction of investment in comprehensive early <br> Due to the growth of the system pressure moderation and VAV boxes and other elements of the cost .of the equipment control will be improved. But as VAV system can be distributed according to cooling load and thermal load, so that the air in buildings within the temperate zone transfer between a balanced, so that the system is designed to reduce the total air, .so you can reduce the volume of the air-conditioning system of the equipment, systems and integrated initial investment divergence will increase even reduces. <br> 9, VAV system layout is simple, maintenance workload small, long service life. <br> Second ., VAV system (VAV) Temperance principles <br> VAV control and room temperature controller comprise indoor cascade abstinence, accepted the indoor temperature-controlled quantity of air flow amount for secondary abstinence. <br> - For VAV abstinence as the room temperature sensor .detects the actual temperature, and set the temperature difference than the ability to output the required air flow adjustment signal, its cure for VAV air valve at the end of it, and change the air so that the links in the indoor temperature setting range. < .br> At the same time, airway pressure sensor to detect the duct outlet pressure change, accepted the PI or PID controlled by frequency converters and curing, VAV air blower speed, eliminating the effects of stress turbulence, air. <br> Third, VAV .system (VAV) often use moderation style pattern <br> 1. fixed static pressure moderation <br> Working principle: ensuring system at a point in the wind (or some parity) static pressure must be the premise of the indoor air volume required by .VAVBOX air valve therapy; system air pressure inside the duct and the points of difference that set values Temperance converter work its cure fan speed. At the same time, you can change the air temperature to glut indoor comfort requirements. <br> Second, the .variable static pressure moderation <br> Working principle: ensuring VAVBOX air valve made possible in the full open position (85-100%), the system air supply from wind in the static pressure to limit the frequency converter, its cure fan speed. At .the same time, you can change the air temperature to glut indoor comfort requirements. <br> III. total air volume control <br> Working principle: by changing the air adjustment of indoor temperature and the air supply and return air's constant difference links to .glut built from exhaust requirements. <br> Fourth, Vav (VAV) system basic Constitution <br> 1, indoor VAV controller <br> The end of the second, Vav (VAVBOX) - with restraint device, sensor, air valve, BOX .boxes and otherAuxiliary facilities <br> 3. air duct pressure measuring device <br> Fourth, VAV air conditioner (with inverter) <br> V. Vav (VAV) air conditioning system development trends <br> Foreign luxury office building in general are .the VAV system as an essential system and General rejected FC + fresh air system, "let FC to return to the hotel from the beginning to" is this the best thesis. Notification of the CBDs trends will be VAV system because VAV system in technical, .economic, illustrations, maintenance of small aspects have incomparable advantages. <br> 6. the principle of VRV systems and features conditioing is in power and air conditioning system, the refrigerant compressor through moderation of reincarnation and into the Interior heat exchanger of refrigerant flow, .degeneracy when we made to glut Interior cooling load and thermal requirements of efficient refrigerant air conditioning system. Its working principle is: the moderation system enlisting indoor comfort parameters, outdoor environment parameters and characterization of the refrigeration system health state parameters, according to the system running .the optimization criteria and guidelines for physical comfort, healing by variable frequency etc.-eye and air compressor to lose self-control air conditioning system with fan, electronic expansion valve, all controllable devices that guarantee comfort the indoor environment, and air conditioning system unchanged .Ding for in top working condition. <br> VRV system with an energy-saving and comfort of the effectiveness of the system based on the difference in indoor load, speed running, reduced due to frequent start-up and shutdown of the compressor to the .amount of loss; accept + compressor start work at low frequency, reduce start operating current, electric equipment will significantly save energy while stopped on other electrical equipment and electric blow; have healing properties of the volume of energy, improved indoor comfort. <br> .VRV system with a design and installation of facilitation, placement with a plot and changeable, 『_I family built space is small, the massive use of facilitation, depend on the risk of living and low running cost, no House, no water system and other .strengths. <br> Seven, VRV systems in engineering design should pay attention to the issue of problem 2.1 fresh air conditioning system, new air flow is a very important technical parameters, but also achieve indoor health scales. Currently used in the fresh air style .patterns are: <br> (1), use a dedicated new fan, its interior design by fresh air cycle machine, pipe number for 6 or 8, wind pressure is quite high, but the price is very high, generally less accepted in engineering .; <br> (2) total heat exchanger with fresh air. This kind of split type structure in line with exhaust requirements appropriate occasions, such as restaurant and entertainment, meetings room, etc. At the end of the top outdoor fresh air ventilator and .outdoor exhaust heat and moisture Exchange held back into the room, you can reduce the load on the fresh air, an adult is energy conservation. <br> However, in the project design needs to focus on new air inlet and outlet of the placement must .be reasonable, particularly polluting places, but also to consider the fresh air and exhaust air pollution problems at Yi, when used in the Caspian Sea, as most of the few urban air quality is poor, ash, filters easy to plug, often wash filter .. <br> (3) chassis with the wind will be fresh to various indoor and outdoor air load borne by each of the indoor unit. The simple style pattern system, and designed the wind also in accordance with the requirements of the system chassis is .very easy to choose the right air pressure. The transitional seasons can also be used as an airless ventilator. But not the end of the processing of fresh top direct access, indoor and outdoor air separate when processing system compared to the indoor unit designation with fire ., noise also increase fire and in outdoor air and moist degree is large, indoor unit may be bred condensation phenomenon occurs. <br> From here we can see on conditioing most intractable problem of fresh air, all cases are recommended to accept a third processing .style pattern, economic reasonable, simple combination. Where exhaust requirements of occasions, the priorities of the second kind of split type structure. <br> 2.2 VRV system own limitations <br> (1) the maximum number of connections to outdoor unit; 4 .<br> (2) maximum outdoor machine portfolio volume to 48HP: <br> (3) the maximum number of connections to indoor-40; <br> (4) of indoor and outdoor machine volume ratio 50% ~ 130 per cent: .<br> (5) maximum actual pipe length is 150 meters; <br> (6), exterior and interior machine maximum drop when outdoor machine in the 50 m on, when the outdoor unit in under 40 m; <br> (7 .) maximum total piping length is 300 m. <br> 2.3 indoor unit selection of a project in some parts of the indoor use inappropriate, such as: 1. a project in a small elevator Hall use embedded on all of the indoor air; 2 .. a project on the suspended ceiling the following installation hanging out in the indoor unit, improperly, should use mosaic double or four air indoor machine: 3. a project in an area of great Hall, the choice of several four air of indoor unit, .the actual selection subsurface mounted wind tube indoor machines will not only reduce expenditure on investment, you can also plot with interior finish placement air reaches the use purpose. <br> Recommendations: <br> 1. room ceiling, and flat growth in narrow- .mining just half-Ming installed four air indoor unit. <br> 2. have hanging items and plane square or larger space accept half-Ming installed four air indoor unit, when the plane space is large, in order to cut costs or more masters .with interior finish selection subsurface mounted may also accept type indoor unit. <br> 3. room no ceiling, in accordance with its expanding Planar shapes, masters admitted that mounted hanging, Ming Siu-Ming loaded and mounted floor type indoor unit. <br .> 2.4 outdoor machine power consumption issue VRV product samples provided by the compressor power transmission cannot be regarded as the power consumption of the compressor, both between mechanical and electrical efficiency, usually 0.8. <br> 2.5 room table machine made of practical engineering, particularly .small and medium scale projects in the same plane, there are a number of function rooms, the use of time differences, and also the smaller area (eg, small meeting room, welcome room, balcony, small restaurants, etc.), to make .a reality of air conditioning systems division than force hard, even though the sword can be done while the system is also very large. .If you accept the above VRV system is simple and fully reflects its placement of both masters and throttling broad characteristics of running costs. The difference is to use the features and differences of time in the same room with air conditioning system, so that there is room .for reasonable people better suited, and this requires consideration of both the problem of using coefficient, and how using coefficient as the case may be, but indoor and outdoor machine volume ratio is not less than 50 per cent, also cannot span 130 per cent. .<br> 2.6 outdoor machine placement problems of the placement of the outdoor unit should glut the following requirements: no air intake conda nuisance exhaust smooth without recirculation. Only do this one can guarantee the outdoor unit of cold (heat). Outdoor unit placement on .the roof, Sun terrace and on the ground, the front two practices, both have advantages and disadvantages: <br> Outdoor unit placement in the roof, the roof is empty the strengths: wide, smooth air, hot air emission to air soon. .Disadvantages: the wind turns, when numerous outdoor unit placement during the same roof, air intake more twists and turns and nuisance. Outdoor unit placement during the drying stage duration: air smoothly. Disadvantages: the exhaust is not smooth, reflow phenomenon, when several .vertical placement, easy formation following outdoor machine top exhaust air is inhaled as an outdoor unit, unit producing air cooling capacity (heat). <br> 2.7 condensate pipe installation problems VRV sector indoor leucorrhea condensate drain pump, this design brings splashing day facilitate. .In fact, the length of the condensate pipe process should only take care of even short, and to have a gradient of 0.O1, to avoid the formation of gas resistance, drainage is not smooth. If not enough of the condensate pipe slope pipe ., made of a water lift tube. Lift tube height should be less than the various models of the height of the condensate drain l of value. Lift tube from the tube indoor unit should be small problems because 300mm.2.8 refrigerant VRV system of pipe joints ., increase the possibility of a refrigerant leak, and the system's internal volume is too large, increase the amount of the refrigerant, the air conditioner installation room requirements designed to: when rendering a refrigerant leak, their concentrations do not cross the limits. To refrigerant .R410A, for example, it is not toxic attitude mild retardation, but when concentrations rise there infarction risk. It is about the limit concentration: refrigerant quantity (kg) / install indoor room minimum volume (m3) ≤ concentration limit (kg / cubic metre .) for a drag-and-much refrigerant concentration limit 0.3 kg / m³. Concentration limits are likely across the room, and the adjacent room to have a say, or installed with gas leak detection devices chain of mechanical ventilation equipment. <br> < .br> <br>.