Building Cooling and Heating Load Calculations
Comprehensive university textbook unit covering fundamental principles, governing relationships, and engineering applications of Building Cooling and Heating Load Calculations.
§5.1 Envelope conduction and thermal bridges
**Outcome:** Interpret envelope conduction and thermal bridges, perform a traceable estimate, diagnose a limitation, and explain how evidence could change the associated engineering decision.
§5.2 Solar gains through glazing
**Outcome:** Interpret solar gains through glazing, perform a traceable estimate, diagnose a limitation, and explain how evidence could change the associated engineering decision.
§5.3 Occupant, lighting and equipment loads
**Outcome:** Interpret occupant, lighting and equipment loads, perform a traceable estimate, diagnose a limitation, and explain how evidence could change the associated engineering decision.
§5.4 Outdoor air and infiltration loads
**Outcome:** Interpret outdoor air and infiltration loads, perform a traceable estimate, diagnose a limitation, and explain how evidence could change the associated engineering decision.
§5.5 Design-day peak versus annual energy
**Outcome:** Interpret design-day peak versus annual energy, perform a traceable estimate, diagnose a limitation, and explain how evidence could change the associated engineering decision.
Step-by-Step Refrigeration and Air Conditioning Solutions
Three original questions connect calculations, definitions and interpretation. Open each solution to follow the reasoning.
Problem Statement: An engineering practitioner analyzes a mechanical system governed by **Envelope conduction and thermal bridges** under steady operational loading.
Worked Engineering Derivation:
**Assumed inputs and computed answer:** A 45 m² facade with U=0.65 W/(m² K) and 12 K temperature difference transmits roughly 351 W in the steady approximation. Reproduce the result using the equation rather than copying the displayed answer. Convert all values to compatible units before substitution. Distinguish kW from kWh, kPa from Pa, and a percentage from a dimensionless fraction. Then perform three small checks: does the output have the expected dimensions, is its sign physically meaningful for the chosen reference direction, and does it approach a sensible limiting value when the driving difference or mass flow tends toward zero? If a limiting case gives a contradiction, examine the equation and model boundary before trusting the decimals.
Problem Statement: An engineering practitioner analyzes a mechanical system governed by **Solar gains through glazing** under steady operational loading.
Worked Engineering Derivation:
**Assumed inputs and computed answer:** With 12 m² glazing, incident 500 W/m² and solar heat-gain coefficient 0.35, simplified gain is 2.10 kW. Reproduce the result using the equation rather than copying the displayed answer. Convert all values to compatible units before substitution. Distinguish kW from kWh, kPa from Pa, and a percentage from a dimensionless fraction. Then perform three small checks: does the output have the expected dimensions, is its sign physically meaningful for the chosen reference direction, and does it approach a sensible limiting value when the driving difference or mass flow tends toward zero? If a limiting case gives a contradiction, examine the equation and model boundary before trusting the decimals.
Problem Statement: An engineering practitioner analyzes a mechanical system governed by **Occupant, lighting and equipment loads** under steady operational loading.
Worked Engineering Derivation:
**Assumed inputs and computed answer:** Twenty occupants assumed at 80 W sensible each, 0.7 kW lighting and 1.2 kW equipment produce 3.5 kW sensible gain. Reproduce the result using the equation rather than copying the displayed answer. Convert all values to compatible units before substitution. Distinguish kW from kWh, kPa from Pa, and a percentage from a dimensionless fraction. Then perform three small checks: does the output have the expected dimensions, is its sign physically meaningful for the chosen reference direction, and does it approach a sensible limiting value when the driving difference or mass flow tends toward zero? If a limiting case gives a contradiction, examine the equation and model boundary before trusting the decimals.
Problem Statement: An engineering practitioner analyzes a mechanical system governed by **Outdoor air and infiltration loads** under steady operational loading.
Worked Engineering Derivation:
**Assumed inputs and computed answer:** At 0.18 kg/s outdoor dry air and a 10 K difference, sensible outdoor-air load is about 1.81 kW. Reproduce the result using the equation rather than copying the displayed answer. Convert all values to compatible units before substitution. Distinguish kW from kWh, kPa from Pa, and a percentage from a dimensionless fraction. Then perform three small checks: does the output have the expected dimensions, is its sign physically meaningful for the chosen reference direction, and does it approach a sensible limiting value when the driving difference or mass flow tends toward zero? If a limiting case gives a contradiction, examine the equation and model boundary before trusting the decimals.
Problem Statement: An engineering practitioner analyzes a mechanical system governed by **Design-day peak versus annual energy** under steady operational loading.
Worked Engineering Derivation:
**Assumed inputs and computed answer:** For 8 kW mean cooling over 500 h at COP 4, estimated electricity use is 1000 kWh, excluding other loads. Reproduce the result using the equation rather than copying the displayed answer. Convert all values to compatible units before substitution. Distinguish kW from kWh, kPa from Pa, and a percentage from a dimensionless fraction. Then perform three small checks: does the output have the expected dimensions, is its sign physically meaningful for the chosen reference direction, and does it approach a sensible limiting value when the driving difference or mass flow tends toward zero? If a limiting case gives a contradiction, examine the equation and model boundary before trusting the decimals.