EKS-HUM-017 / Moisture load and airflow

Sensible Heat Ratio

显热比

Sensible heat ratio is the sensible heat-transfer rate divided by the sum of sensible and latent heat-transfer rates for the same process.

Abbreviations: SHR, SHF
Aliases: sensible heat factor

QUANTITY, SYMBOL AND UNIT

Quantity / objectSensible heat ratio

SymbolSHR, SHF

SI1dimensionless ratio

Common%percent

Definition

Sensible heat ratio is the sensible heat-transfer rate divided by the sum of sensible and latent heat-transfer rates for the same process.

SHR describes the balance between temperature load and moisture load. A lower value indicates a larger latent share, but the ratio must always be accompanied by the total load or both component loads.

Formula and variables

SHR = q_s / (q_s + q_l)

Conditions: Sensible and latent rates must use the same system boundary, time basis and sign convention. For ordinary positive cooling-load components, SHR lies between 0 and 1.

Symbol	Meaning	Unit
`SHR`	sensible heat ratio	1
`q_s`	sensible heat-transfer rate	W
`q_l`	latent heat-transfer rate	W

Relations and distinctions

SHR and latent fraction

For the same positive load convention, the latent fraction is 1 minus SHR. It is not the moisture mass-removal rate.

Space SHR and equipment SHR

Space SHR describes the application load. Equipment SHR describes performance at a stated operating point; matching requires more than comparing one ratio.

Engineering meaning

Use SHR to communicate the sensible-versus-latent balance after both loads have been calculated.
Check whether equipment can meet the latent component at the actual entering state, not only the total capacity.

Common misconceptions

MisconceptionThe same SHR always represents the same dehumidification requirement.

Accurate explanationThe same ratio can accompany very different total loads, moisture rates and operating conditions.

Application boundaries

SHR is invalid if the numerator and denominator use different system boundaries or signs.
SHR alone cannot determine airflow, moisture removal, leaving-air state or equipment size.

Supporting sources

ASHRAE / SRC-ASHRAE-TERMINOLOGY-S

ASHRAE Terminology: Sensible Heat and Sensible Heat Ratio ↗

/ Entries for sensible heat and sensible heat ratio
Supports: SHR is sensible heat divided by sensible plus latent heat for a process; SHR is dimensionless; Sensible heat factor is an alternate term
ASHRAE / SRC-ASHRAE-F25-CH18

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

2025 SI edition / Chapter 18, Section 1, sensible and latent heat-flow distinction
Supports: Sensible and latent loads are separate components of total heat load; Equipment can have different sensible and latent removal capabilities

Maintenance record