Cork Institute of Technology. Autumn 2006 Building Services Mechanical Paper 1 (Time: 3 Hours)

Transcription

1 Cork Iniue of Tehnology Bahelor of Engineering in Building Servie Engineering ward NFQ - Level 7 uumn 2006 Building Servie Mehanial Paper Time: 3 Hour Inruion Examiner: Dr. N. J. Hewi nwer FOU queion. Mr. D. Leonard ll queion arry equal mark Mr. F. Delaney Q. Wrie an eay on ombined hea and power. Your eay hould over a a minimum: operaing priniple of CHP, benefi of CHP, hea o power raio, prime mover, building hea and elerial profile, ypial appliaion. 25 mark Q2. n offie blok oni of 3 floor wih 5 offie per floor. ume all offie are idenial wih 4.0 kw of enible gain and 0.4 kw of laen gain. There are 6 people per offie wih a freh air requiremen of 2 lire per eond per peron. The offie are o be mainained a 22 o C, 50% auraion. The ouide air i a 30 o C dry bulb and 23 o C we bulb. ir i o be upplied o he room a 3 o C by a enral HU whih ake in ouide freh air and mixe hi wih reirulaed air from he offie. a Calulae he volumeri flow rae of upply air. 4 mark b Calulae he volumeri flow rae of ouide freh air. 3 mark Calulae he volumeri flow rae of reirulaed air. 2 mark d Calulae he emperaure of he mixed air. 4 mark e Calulae he moiure onen of he upply air. 4 mark f Plo he ouide, room, upply and mixed air ae on he pyhromeri har and reurn i wih your anwer book. 3 mark g Calulae he ooling oil load. 5 mark SH kw 273 V 35 r LH kw 273 V g g 860,000 r

2 Q3. refrigeraion yem, working on he vapour ompreion yle, develop 35 kw of refrigeraion. The ondening emperaure i 30 C and he evaporaing emperaure i - 5 C. The refrigeran leave he ondener in he auraed ae and refrigeran leave he evaporaor wih 5 C uperhea. a Skeh he hemai for he yem and mark he proe on he aahed P-H har. Plae your name on he har and reurn i wih your anwer book. 4 mark b Calulae he refrigeraing effe in kj/kg. 4 mark Calulae he ma flow rae of refrigeran in kg/. 4 mark d Calulae he oeffiien of performane. 4 mark e Calulae he heoreial ompreor in kw. 4 mark f Deribe uing a nea keh he operaion of a hermoai expanion valve. 5 mark Q4. a Sae 3 reaon why ondenae in eam yem hould be olleed and reurned o he boiler. 3 mark b Wha i he purpoe of blowdown in eam boiler? 2 mark eam boiler work a 0 bar g produing 6000 kg/hr. The maximum allowable TDS i 2500 ppm and he feedwaer TDS i 300 ppm. Blowdown i reurned o a flah reovery veel operaing a 0.5 bar g I. Calulae he boiler blowdown rae. 3 mark II. Calulae he oal energy in he blowdown 4 mark III. Calulae he perenage of flah eam generaed 4 mark IV. Calulae he oal energy in he flah eam 3 mark V. Calulae he oal energy in he ondenae from he flah reovery veel. 3 mark VI. Size he flah reovery veel 3 mark 2

3 Q5. a Define he erm dry reulan emperaure and mean urfae emperaure. 2 mark b Deribe how he imple eady-ae model ake ino aoun he dry reulan emperaure and perenage of radiaion from differen emier in aeing hea lo from a ruure. 4 mark high emperaure radian yem i o be inalled in a por hall. The radian faor i 0.9. The ruural deail for he enre are given below. The dry reulan emperaure i o be 20 0 C, he ouide air emperaure i -2 0 C, and he infilraion rae i air hange per hour. The building volume i 00 m 3. Calulae he oal hea lo, inernal air emperaure and mean urfae emperaure for he por hall. 7 mark Sruural Deail Elemen rea m 2 U-Value Wm -2 K - Floor oof Exernal Wall Glazing Door d If a fored warm air yem wa ued wha would be he impa on air and mean urfae emperaure be? 2 mark 3

4 4 Formulae [ ] U Cv U C F v [ ] U Cv U U F C C Q v ao v ai ai m 2 ' ' ao U U.93 min 9 m m E E M [ ] [ ] e E e if E M M NM m max min m m min m U O m SHkWx Q r 860, Qx LHkWx g g r

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