EKS-HUM-016 / Moisture load and airflow

Sensible Heat Load

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Sensible heat load is the rate of heat addition or removal associated with changing or maintaining dry-bulb temperature without counting moisture phase change.

Aliases: sensible load

QUANTITY, SYMBOL AND UNIT

Quantity / objectSensible heat load

Symbolq_s, Q_sen

SIWwatt

CommonkWkilowatt

IPBtu/hBritish thermal unit per hour

Definition

Sensible heat load is the rate of heat addition or removal associated with changing or maintaining dry-bulb temperature without counting moisture phase change.

For a space it can arise from the envelope, lighting, equipment, people and outdoor air. It is expressed as power and is evaluated separately from latent load because equipment handles temperature and moisture at different rates.

Formula and variables

q_s = ṁ_da (c_pa + W c_pv) Δt

Conditions: Steady airflow sensible-heat relation using a consistent dry-air mass basis and a stated temperature interval. Property values must match the operating range.

Symbol	Meaning	Unit
`q_s`	sensible heat-transfer rate	W
`ṁ_da`	dry-air mass-flow rate	kg_da/s
`c_pa`	specific heat of dry air	J/(kg_da·K)
`W`	humidity ratio	kg_w/kg_da
`c_pv`	specific heat of water vapour	J/(kg_w·K)
`Δt`	dry-bulb temperature difference	K

Relations and distinctions

Sensible and latent load

Sensible load is tied to dry-bulb temperature change; latent load is tied to water-vapour addition or removal and phase change.

Sensible load and total load

Total heat load combines sensible and latent components on the same sign, time and system boundary.

Engineering meaning

Use sensible and latent design loads together when checking supply-air state and equipment operating mode.
Retain actual airflow, density or mass-flow and altitude basis instead of relying on an unexplained shortcut constant.

Common misconceptions

MisconceptionA dehumidifier only responds to latent load, so sensible heat can be ignored.

Accurate explanationRefrigeration, reheat, fan heat and desiccant heat of sorption all affect the sensible balance and leaving-air temperature.

Application boundaries

A space load and a coil load are different boundaries and may not be numerically equal.
The simple airflow formula does not replace a complete transient building or process heat balance.

Supporting sources

ASHRAE / SRC-ASHRAE-F25-CH18

ASHRAE Handbook - Fundamentals, Chapter 18: Nonresidential Cooling and Heating Load Calculations ↗

2025 SI edition / Chapter 18, Section 1 and airflow heat Equations 8–9
Supports: Sensible heat changes dry-bulb temperature without representing moisture addition; Sensible heat load is an energy rate; Airflow sensible load depends on mass flow, heat capacity and temperature difference

Maintenance record