Cooling loads, psychrometrics, air systems and refrigeration cycles.
MODULE OVERVIEW
HVAC & Refrigeration in practical engineering work.
HVAC design maintains indoor conditions through controlled heat, moisture and air movement. Area-based cooling loads can establish an early allowance but cannot replace a room-by-room load calculation.
CORE PRINCIPLES
What to establish first
Envelope, solar, people, equipment and ventilation each contribute to load.
Sensible and latent loads must be separated for air treatment.
Equipment selection uses design conditions, diversity, controls and part-load performance.
DESIGN CONCEPTS
Terms worth checking
Cooling load
Psychrometrics
Ventilation
Common applications: Early equipment budgeting · Small comfort-cooling concepts · Comparing concept layouts
KEY RELATIONSHIP
Area-based preliminary cooling load
Q = A × qdesign
A — conditioned area, m²
qdesign — selected load density, W/m²
Q — preliminary load, W
The load density is a planning assumption, not a substitute for envelope and occupancy calculations.
Use the relationship with compatible units, then review the result against the stated design conditions.
WORKED EXAMPLE
Known values → substitution → interpretation
Known values
A = 120 m²; qdesign = 130 W/m²
Method
Q = 120 × 130
Interpretation
The initial allowance is 15.6 kW, approximately 4.44 TR.
KEY DESIGN CHECKS
Confirm the conditions behind the number
Define the governing load case, duty cycle and required design life before using a simplified relation.
Use compatible units and material data for the actual condition, temperature and manufacturing state.
Compare the result with strength, stiffness, fatigue, safety, serviceability and applicable-code requirements.
COMMON ENGINEERING MISTAKES
Keep the model within its scope
Applying area-based preliminary cooling load outside the assumptions shown on this page.
Using a nominal condition while a peak, alternating, transient or environmental case governs the design.
Treating a calculated value as a final component selection without checking interfaces, tolerances and the current governing standard.
ReferenceASHRAE Handbook—Fundamentals; consult the current edition and local energy code for design.ScopeRelationships are presented for the assumptions stated on this page and linked tool.Design reviewCheck material condition, loads, environment and the applicable current code.SafetyResults are educational/preliminary and do not certify safety or compliance.
