15.18 The building in Example 15.5 can be heated ei by the boiler specified in t

Question

15.18 The building in Example 15.5 can be heated ei by the boiler specified in the example or by two boilers, one with one-third the example b capacity and one with two-thirds the capacity Both have the same part-load characteristicsa the boiler in Example 15.5. Since the boiler in the example has more capacity than needed most of the time, less energy may be used with smaller boilers operating more closely to their full capac- ity. Add the columns needed to the spreadsheet in Table 15.5 to study this option. For simplicity assume that the smaller boiler operates up to full capacity before the second is activated. (4) oiler

Explanation / Answer

Ans: We have to find Average effieciency, PLR, Heat input and heat produced by boiler at 37.50C.

Step 1. Using HCB Software we have the following data.

consider Bin temperature at 250F, so Effieciency will become,

PLR which is ratio of standard load to peak load will be

PLR=3000/7000 (Peak load at 37.50F)

PLR= 0.428

and Q/Qfull= 0.1+1.6*0.428-0.7*0.428*0.428= 0.65

Boiler input at rated conditions will be 8750KW

so Q=0.65*8750=5747KW.

and Boiler effieciency will be

0.522

Finally fuel consumed will be the product of energy input*no of operating hours.

Qinput=5747*758h= 4356MBtu hr

and heat produced by boiler ist the product of heat produced at standard operating conditions * no of operating hours

Qheat= 3000*758h=2274MBtu/hr

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