Problem 12.7: An 800ton chiller operates at 060 kWton under

From Chapter 12 Problem Set. Level 2: Applied Thinking.

Question

An 800-ton chiller operates at 0.60 kW/ton under clean conditions for 4,500 hours per year at $0.11/kWh. Condenser tube fouling has increased the approach temperature by 4°F. Using the upper-end estimate (2% energy increase per °F of approach rise), calculate:

1. Annual energy cost under clean conditions.
2. Annual energy cost under fouled conditions.
3. The annual cost penalty from fouling.

Answer

Show answer

Clean conditions: 800 tons × 0.60 kW/ton = 480 kW. Annual energy = 480 × 4,500 = 2,160,000 kWh. Annual cost = 2,160,000 × $0.11=\ast \ast$237,600**. Fouled conditions: 4°F × 2% = 8% energy increase. Additional power = 480 × 0.08 = 38.4 kW. Total = 518.4 kW. Annual energy = 518.4 × 4,500 = 2,332,800 kWh. Annual cost = 2,332,800 × $0.11=\ast \ast$256,608**. Annual penalty from fouling = $256,608-$237,600 = $19,008.