PROFESSIONAL ENGINEERS OF ONTARIO. ANNUAL EXAMINATIONS May Mec-B2 Environmental Control in Buildings. 3 hours duration

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ANNUAL EXAMINATIONS My 201 S Pge 1 of 7 07-MEC-B2 Environmentl Control in Buildings PROFESSIONAL ENGINEERS OF ONTARIO ANNUAL EXAMINATIONS My 2015 07-Mec-B2 Environmentl Control in Buildings 3 hours

1 ANNUAL EXAMINATIONS My 201 S Pge 1 of 7 07-MEC-B2 Environmentl Control in Buildings PROFESSIONAL ENGINEERS OF ONTARIO ANNUAL EXAMINATIONS My Mec-B2 Environmentl Control in Buildings 3 hours durtion INSTRUCTIONS: 1. If doubt exists s to the interprettion of ny of the questions, the cndidte is urged to submit cler sttement of the ssumptions) tht he/she hs hd mde with the nswer. 2. The exmintion pper is open book nd so cndidtes re permitted to mke use of ny textbooks references or notes tht they wish. 3. Any non-communicting clcultor is permitted. The usge of computers, Internet nd smrt phones is prohibited. 4. Cndidtes re expected to hve copies of both n environmentl control book nd stem tbles, since it will be necessry to use informtion presented in the tbles nd grphs contined in books. 5. Cndidtes re required to solve five questions. 6. All questions crry the sme vlue. Indicte which five questions re to be grded on the cover of the first exmintion workbook. 7. Psychrometric chrts nd the p-h digrm for the refrigernt re ttched.

ANNUAL EXAMINATIONS My 201 S Pge 2 of 7 07-MEC-B2 Environmentl Control in Buildings PROBLEM 1. (20 POINTS) A zone in building hs sensible lod of 20.5 kw nd ltent lod of 8.8 kw.

2 ANNUAL EXAMINATIONS My 201 S Pge 2 of 7 07-MEC-B2 Environmentl Control in Buildings PROBLEM 1. (20 POINTS) A zone in building hs sensible lod of 20.5 kw nd ltent lod of 8.8 kw. The zone is to be mintined t 24 C nd 50 / reltive humidity (RH), with n ir supply to the room of 1.8 kg/s t 14 C nd 60% reltive humidity. The outside design conditions re 28 C nd 70 / reltive humidity. The p11nt consists of mixing chmber for re-circulted nd outside fresh ir, cooling coil supplied with chilled wter, heting coil nd supply fn. The rtio of re-circulted ir to fresh ir is 3:1; the cooling coil hs n pprtus dew point of 5 C, nd the refrigertion unit supplying the chilled wter hs n overll coefficient of performnce of 2. Neglect ll friction losses nd fn nd pump work. Assume se level conditions.. Drw digrm of the system. b. Drw the operting cycle on the psychrometric chrt provided. c. Identify ech significnt point, on the digrm nd psychrometric chrt, nd note for ech of these points its dry bulb nd wet bulb temperture. d. Clculte the totl ir conditioning lod for the room. e. Clculte the totl energy input. f. Clculte the required energy input if the energy to the heting coil is supplied from the refrigertion plnt condenser cooling wter. PROBLEM 2. (20 POINTS) An ir conditioning system operting on the winter heting cycle, is required to mintin inside conditions of 68 FdB (dry bulb), 50% RH (reltive humidity), when the outdoor design conditions re 32 FdB nd 10% RH. The sensible het loss from the building is 220,000 Btu/hr, nd the ltent het loss is 45,000 Btu/hr. The building will be heted using heter nd stem humidifier. The mss rtio of outside ir to the mixed ir is The supply ir tempertut e is 100 Fd13. The stem humidifier uses sturted stem t 20 Asi.. Identify ech chrcteristic point on the digrm, b. Drw the operting cycle on the psychrometric chrt provided, nd show for ech significnt point its dry bulb temperture nd reltive humidity. c. Determine the supply ir conditions nd quntity (Ib/hr) d. Clculte the Btu/hr rting of the heter. e. Clculte the mss flow rte of stem. PROBLEM 3 (20 POINTS). A centrifugl fn operting t 2400 rpm delivers 20,000 cfm of ir through 32 inch dimeter duct ginst sttic pressure of 4.8 in. HZO. The ir is t 40 F. The brometric pressure is 29.0 in. Hg.. Clculte the power, if the efficiency is 70%. b. If the fn size, gs density, nd duct system remins the sme, clculte the power required if the fn is operted t 3200rpm. c. Explin the effect of ir density on the flow rte, developed hed nd horsepower.

ANNUAL EXAMINATIONS My 201 S Pge 3 of 7 07-MEC-B2 Environmentl Control in Buildings PROBLEM 4. (20 POINTS). 10 points Indoor ir qulity is one of the mjor concerns in HVAC industry tody.

3 ANNUAL EXAMINATIONS My 201 S Pge 3 of 7 07-MEC-B2 Environmentl Control in Buildings PROBLEM 4. (20 POINTS). 10 points Indoor ir qulity is one of the mjor concerns in HVAC industry tody. Plese describe in mximum of two pges wht re the fctors influencing the indoor ir qulity, nd wht mesures re to be tken in order to provide n cceptble indoor ir qulity. In your discussion mke reference to stndrds nd codes required in mintining n cceptble indoor ir qulity. b. IO points Suppose there is source of NOx in building tht produces 110 µg/s of NOx. If the ir inside the building is lwys well mixed, nd if the outdoor ir hs llredy NOx concentrtion of 50 µg/m3, wht outdoor irflow is needed to stisfy the required (recommended by stndrd) conditions in the building. PROBLEM 5. (20 POINTS) The wll of house consists of two 125mm thick brick wlls with n inner cvity. The inside wll hs 10 mm coting of plster nd there is cement rendering of 5 mm on the outside wll. In one room of the house the externl wll is 4 m x 2.5 m, nd contins window of 1.8 m x 1.2 m of 1.Smm thick glss. The het trnsfer coefficients for the inside nd outside surfces of the wll nd window re 8.5 nd 31 W/m2K, respectively. The therml conductivities of bt ick, plster, cement nd glss re 0.43, 0.14, 0.86, nd 0.76 W/m K, respectively. Clculte the proportion of the totl het trnsfer which is due to the het loss through the window. Assume tht the resistnce of the ir cvity is 0.15 mzk/w. Neglect ll end effects, nd neglect rdition. PROBLEM 6. (20 POINTS) A smll size induced (forced drft) cooling tower is designed to cool 6 liters of wter per second, with the inlet temperture of 45 C. The motor driven fn induces 9 m3/s of ir through the tower nd the power bsorbed is 4.75 kw. The ir entering the tower is t 18 C, nd hs reltive humidity of 60%. The ir leving the tower cn be ssumed to be sturted nd its temperture 26 C. Show digrm of the cooling tower. Clculte the finl temperture of the mount of cooling wter mke-u~ required per second. Assume tht pressure remins constnt throughout the tower t br.

4 ANNUAL EXAMINATIONS My 201 S Pge 4 of 7 07-MEC-B2 Environmentl Control in Buildings PROBLEM 7. (20 POINTS) A smll commercil building locted in Toronto, Ontrio hs heting lod of 75 kw sensible nd 12 kw ltent. Design conditions re 22 C nd -20 C. The structure is heted with nturl gs wrm-ir furnce, with n efficiency of 85%. Clculte the yerly heting fuel requirements. An energy contrctor fter n energy udit of the building, suggested to the owner of the bove building, to instll het pump. The contrctor clims tht the het pump hs COP (coefficient of performnce) of The compressor/motor hs n efficiency of 82%. Drw schemtic s how n ir to ir het pump will provide the heting lod. Do you know of ny other types of het pumps? Explin. Wht will be your dvice to the building owner? Mke ssumptions s to the cost of nturl gs nd electric energy, nd bse your nswer on good engineering prctice, considering environmentl impct for ech solution. PROBLEM 8. (20 POINTS). 15 points An idel R134 chiller opertes with condensing temperture of 125 F nd n evportor temperture of 35 F. If the cooling rte is 20 tons, wht re the refrigernt flow rte, condenser pressure, evportor pressure, nd COP? Compre the COP with tht of Crnot refrigertion cycle operting between the sme condensing nd evporting tempertures. b. 5 points Wht re the primry environmentl concerns relted to the use of refrigernts.

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Psychrometric Applications

Psychrometric Applications Psychrometric Applictions The reminder of this presenttion centers on systems involving moist ir. A condensed wter phse my lso be present in such systems. The term moist irrefers to mixture of dry ir nd