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Boss lesson · The Plant Room Final
Exam-hall rules, last plant of the shift
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Exam-hall rules, last plant of the shift

This is the boss. No calculator. Tonight a ton is 3.5 kW3.5\ \mathrm{kW}, ρc\rho c for water is 4.2 kJ4.2\ \mathrm{kJ} per litre per degree, and the evaporation coefficient stays at 0.0018 per °C of range — round numbers every plant engineer keeps for mental work and site sanity checks, and the values are chosen to fit in your head.

One chiller, one tower, one long problem, and every answer feeds the next: tonnage, then heat rejection, then the condenser water that carries it, then the evaporation that flow produces, then the verdict. Write each line down as you go — one early slip rolls all the way to the drain.

And note what the last line actually asks. It does not want another number; it wants a DECISION about the bleed, the way a service call really ends. The arithmetic is only there to earn you the right to make it. Remember the two rails: makeup always exceeds evaporation, and cycles are makeup over BLOWDOWN — never over evaporation, because evaporation carries no minerals out at all.

Then bonus marks on the compressor itself, straight off the chart. One rule carries it: a compressor's real enthalpy rise is the ideal rise DIVIDED by its isentropic efficiency, the opposite way to a turbine, and the power is that rise on every kilogram circulated.

Everything in the chapter rides in this one plant room. 5★ under par here is the chapter crown. Clock in.

T=Q˙12,000 BTU/hrT = \frac{\dot{Q}}{12{,}000\ \text{BTU/hr}}

  • TT= Tons of refrigeration
  • Q˙\dot{Q}= Cooling capacity (power)
Tons of Refrigeration from BTU/hr solver →
HRFQeQr

Qr=Qe HRFQ_r = Q_e \, \mathrm{HRF}

  • QrQ_r= Heat rejection rate (power)
  • QeQ_e= Evaporator (cooling) load (power)
  • HRF\mathrm{HRF}= Heat rejection factor
Chiller Heat Rejection solver →
HRFQV̇ΔT

V˙=Q˙⋅HRFρwcw ΔT\dot{V} = \frac{\dot{Q} \cdot \mathrm{HRF}}{\rho_w c_w \, \Delta T}

  • V˙\dot{V}= Condenser water flow (volumetric flow rate)
  • Q˙\dot{Q}= Evaporator (cooling) load (power)
  • HRF\mathrm{HRF}= Heat rejection factor
  • ΔT\Delta T= Condenser water ΔT (temperature difference)
Condenser Water Flow Rate solver →
ThTcΔT

ΔT=Th−Tc\Delta T = T_h - T_c

  • ΔT\Delta T= Range (temperature difference)
  • ThT_h= Hot water temperature (temperature)
  • TcT_c= Cold water temperature (temperature)
Cooling Tower Range solver →
ERΔT

E=0.001 R ΔTE = 0.001 \, R \, \Delta T

  • EE= Evaporation rate (volumetric flow rate)
  • RR= Recirculation rate (volumetric flow rate)
  • ΔT\Delta T= Cooling range (temperature difference)
Cooling Tower Evaporation Rate solver →
no calculator in the boss room — the numbers are chosen to fit in your head