Implementarea unui sistem de automatizare de tip BMS pentru o centrală de tratare a aerului

1. ABSTRACT

Building Management System (BMS) is one of the heaviest researched areas

motivated by the continuous high demand on economically-effective systems that are designed to provide a desirable controlled space for various organizations. BMS has been developed along with the rapid sophistication of the information and control technologies in this study. The main objective of the continuous effort is to provide an intelligent monitor and control of various facilities within the building so as to offer its users or occupants with effective security, improved productivity, human comfort, and efficient energy management. Heat, Ventilation and Air Conditioning (HVAC), Lighting Systems, Life and Safety System, and Access Control are some of the typical systems that formed BMS in most modern building. HVAC and Lighting systems constitute the major energy consumer in an entire building.

Building management systems (BMS) are extensively utilized in fault detection and isolation (FDI) of heating, ventilating and air-conditioning (HVAC) processes. Usually a BMS, which is directly interfaced to the process only monitors or collects data for the FDI algorithm. Rarely both control and monitoring actions of the automation system are harnessed for FDI. However, in buildings such a diagnostic approach is possible and illustrated in this paper. The fault detection is based on an on-line diagnostic test (ODT), which is a series of control and monitoring actions applied to a process. Performing an ODT means exciting the automated process by using prescribed input signals, supervising responses and comparing results with a process model. All operations are performed on-line, during normal up state of the process and controlled by the automation system. The fault detection method is outlined for an air-handling unit (AHU) and implemented for its preheating process. The approach is demonstrated in a real building by programming the diagnostic algorithms in a BEMS, installed in a college building and further performing test runs. Faults are detected by comparing gathered data with a statistical model. Due to the difficulties in generating natural faults, a few artificial faults were introduced. The test runs show that the ODT is an uncomplicated diagnostic method for finding distinct and abrupt changes in a process but not for detection of slow degradations and gradual faults. Moreover, the ODT seems to be generic over faults and processes, requires no additional instrumentation and no more than domain knowledge for initiation.

2. GENERALITATI

Centralele de tratare aer sunt disponibile in mai multe marimi care pot fi usor selectate folosind diagrama de mai jos, bazata pe viteza aerului prin bobina schimbatorului de caldura.Pentru a simplifica selectia trebuie subliniat ca in ambele cazuri racire/dezumidificare si incalzire/procese de umidificare ,viteza corecta a aerului este esentiala pentru a antrenarea de apa.Prin urmare este recomadat sa folositi separatorul de picaturi pentru umidificarea si dezumidificarea proceselor cand viteza aerului depaseste 2.5 m/s.In umidificare si racire/procesele de dezumidificare,viteza maxima de 2.8 m/s nu trebuie depasita.

Centralele de tratare aer propuse pentru aceasta solutie sunt destinate montajului exterior, in constructie suprapusa, cu structura modulara, in dublu flux cu recuperator de caldura cu placi si clapet de recirculare. Aceasta configuratie functioneaza cu 100% aer proaspat si cu evacuare totala de aer interior, avand posibilitatea comutarii manuale pe recirculare, doar in perioada fazelor de intrare in regim a instalatiei, cand ambientul nu este inca utilizat. Amplasarea clapetului de recirculare dupa recuperator, pe circuitul de evacuare, asigura un circuit aeraulic intotdeauna echilibrat. Activand temporar functionarea cu recirculare totala, cu aceasta dispunere se poate realiza chiar si procesul de dezghetare, atunci cand sunt conditii de formarea ghetii in interiorul recuperatorului.

Centralele de tratare a aerului in discutie sunt construite in conformitate cu normele si directivele Europene si sunt capabile sa satisfaca toate exigentele de proiectare in instalatii de climatizare unde nivelul de zgomot, maxima puritate a aerului si consumul energetic minim reprezinta puncte fundamentale de apreciere.

Principala caracteristica care deosebeste aceasta noua serie, se refera la designul particular al profilelor de aluminiu, ce constituie cadrul centralei, studiat pentru a obtine intreaga suprafata perfect neteda, fara proieminente si punti termice, in scopul usurarii intretinerii si extractiei laterale a componentelor. Structura de baza din profile din tabla zincata de grosime robusta garanteaza maxima stabilitate si o distributie uniforma a greutatii. Executia din panouri sandwich cu grosimea de 50 mm, din tabla zincata cu suprafata exterioara prevopsita si izolatia din poliuretan expandat de inalta densitate, asigura unitatii un grad ridicat de izolare termica si acustica. Fiind configurata pentru amplasare in exterior, este prevazuta cu protectie superioara anti-ploaie.

Circuitul de introducere aer proaspat este constituit din mai multe sectiuni de tratare a aerului, si anume:

• modul de intrare cu registru interior de reglaj;

• sectiune de filtrare, cu filtru sintetic clasa G4 si presostat diferential;

• recuperator de caldura static cu placi din aluminiu si fluxuri de aer incrucisate, calculat pentru temperatura/umiditatea aerului exterior respectiv interior de -15°C/80% respectiv 20°C/50%, rezultand o eficienta > 55%; este echipat cu clapet de recirculare si presostat diferential;