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 Posted: Sat 21:02, 25 Dec 2010 Post subject: ugg stivali VAV air conditioning system terminal d |
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Simulation of VAV air conditioning system terminal device
Degree of fast, high control precision, mainly because the end of the device in addition to temperature control but also have air volume air flow sensor controller, temperature controller based controller,[link widoczny dla zalogowanych], wind controller, deputy controller, the two constitute a cascade control loop thermostat set according to the temperature deviation setting air flow controller, air flow controller based on air volume within the valve bias adjustment terminal device, can quickly compensate for the pressure to maintain the original air flow, the control block diagram shown in Figure - _2. T | _ Room temperature F-Canton room air flow F of a feedback air volume T of a feedback temperature] external disturbance factors in Figure I 2 pressure-independent terminal unit control block diagram of the pressure independent type of terminal devices including air-conditioned room, duct, temperature sensor, air flow sensors, valve, the main controller, deputy controller, therefore, must be established before the simulation of mathematical models of these components. The following list only after the derivation of mathematical model equations of each component: (1) air-conditioned room under the heat balance principle, the room can use the following differential equation: pcv = Q1 + Gc (TS-T) + (T a T) KF (1 ) UL where: T: room temperature, ��; T: outdoor temperature ��; T. : Supply air temperature ��; Ql: indoor load kw; 2004, No. 1 Refrigeration and Air Conditioning 9G-air supply k; K: wall heat transfer coefficient kw / (m2 �� ��); F: external heat transfer area m; V: room volume m; p: air density / m: c: specific heat capacity of air kJ / (kg �� ��). (2) the sensor resistance output temperature sensor commonly used methods, namely, with the input of temperature change in its resistance value, the sensor can be drawn based on heat balance differential equation is:: + (2) where: T2: Feedback temperature ��; Yr room temperature ��:: time constant. (3) the differential equations for the valve actuator: a dC: (3) a = a �� j, dto5 where: C: is the normalized valve stroke; Ci: the control signal: To the maximum signal + Under 0.5 the time required to travel from half 0-1. (4) controller PID controller is the most commonly used controller, the proportional (Proportiona1), points (Differentia1) adjusted for short. PID regulation of the transfer function model: G = (go. S] (4) where: KP: proportional coefficient; TI: the integral time constant: TD: the differential time constant. (5) the transfer air duct air duct function model: G (s):: Fu Dan (5) 2 �� (),. a formula: into: the friction factor along the air duct: de: duct equivalent diameter m; p: air density k coffee: Um : wind speed m / s. 4, drawn by MATIab Bode diagram simulation software based on the above terminal unit derived a mathematical model of each component, combined with the actual�� Cheng,[link widoczny dla zalogowanych], calculated by the following transfer function is derived: the main loop: Room G = an 8 / (260s +1), the temperature sensor Fl: 0.02 / (30s +1). main controller G. = 30 (300s +1) / 300s. Vice circuit: air duct Gl = 2.82,[link widoczny dla zalogowanych], ( Gl varied from 1.54 --- 2.82), the air valve G2: 1/30s, air flow sensor F2 = 0.67 / (s +1). Deputy Controller G. = l0 (10s +1) / 10s through MATIab type of simulation software output pressure independent terminal unit of a simulation shown in Figure 3. _ \ a \ Figure 3, there is a feedback PI control valve end of the device by the Bode diagram Bode diagram shows, the stability margin modulus G = infdB,[link widoczny dla zalogowanych],. crossover frequency ('): infrad / sec, the phase stability margin Pm = 38.7deg, shear frequency ��. v = 1.01rad/sec, see the end of the control loop in a stable range. 5, concluding remarks from This simulation shows that the application of computer simulation technology to the V air conditioning system control circuit debugging facilities to bring a powerful means to avoid the blindness field commissioning, but also solve the economic problems of non-site commissioning, from which we can see computer simulation technology to the broad application prospects. References [1] Liang Zhou Guoqiang and other building energy and HVAC status and development of simulation software Hunan University 2000.12 [2] Ding Guoliang Zhang Road,[link widoczny dla zalogowanych], refrigeration and air conditioning equipment and other intelligent simulation Method of cooling of 1998.2 [3] Zhou Zicheng cooling room air conditioners cooling transient simulation run time of 1999.1 [4] Yang Chen PROCEEDINGS other modeling and simulation of virtual prototyping in the air conditioning compressor in the application of computer Simulation 2003.3 [5] Cai Jing lang \
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