A building with an effective heat conductance – UA of 0.68 kW °Cí1 is occupied for 14 hours from 7h to 20h and unoccupied during the rest of the day. The rates of internal heat gain during the...

A building with an effective heat conductance – UA of 0.68 kW °Cí1 is occupied for 14 hours from 7h to 20h and unoccupied during the rest of the day. The rates of internal heat gain during the occupied and unoccupied periods are 2.85 kW and 0.9 kW respectively. The corresponding indoor temperatures are 22°C and 16°C respectively. The building is heated using a fuel-fired furnace of capacity 14 kW and rated efficiency 88%. The part-load degradation factor of the furnace is 0.25. The hourly ambient temperatures for a particular day are given in Table P13.1.1. Calculate (i) the balance temperatures, and (ii) the energy input to the furnace, during the occupied and unoccupied periods. Plot the energy flow rates versus temperature curves.