Dew-Point vs Temperature Effectiveness in ERV

Temperature effectiveness (sensible)

Temperature effectiveness compares supply temperature change to the maximum possible:

epsilon_T = (T_supply_out - T_supply_in) / (T_exhaust_in - T_supply_in)

This is the number a sensible plate reports, and it is what most generic “efficiency” labels mean.

Dew-point effectiveness (total / enthalpy)

For an enthalpy wheel or membrane, moisture matters, so effectiveness is referenced to the exhaust humidity (dew point):

epsilon_DP = (W_supply_out - W_supply_in) / (W_exhaust_in - W_supply_in)

where W is the humidity ratio. This captures both the temperature and the latent recovery of an enthalpy wheel or 膜式能量回收通风机（ERV）.

Which to quote

For sensible-only units, temperature effectiveness is the honest figure. For total-energy recovery, dew-point (or enthalpy) effectiveness is the right one – quoting only temperature understates the latent saving. Always check which basis a supplier uses when comparing devices.

Frequently asked questions

Can dew-point effectiveness exceed temperature effectiveness? They measure different things; a wheel can have high dew-point effectiveness even when temperature effectiveness is modest.

Which matters for cooling load? Both – but latent (dew-point) recovery is what relieves the cooling coil in humid climates.

Need help specifying the right air-to-air heat recovery for your project? Contact the QIYU engineering team – WhatsApp +86 157 5335 5505, or email kuns913@gmail.com.

常见问题

常见问题

What is temperature effectiveness?

It is the ratio of actual to maximum supply-temperature change using dry-bulb temperatures; the common sensible-effectiveness figure.

What is dew-point effectiveness and when does it differ?

Dew-point effectiveness uses the enthalpy or humidity potential instead of dry-bulb; for enthalpy wheels recovering moisture it can be quite different from temperature effectiveness, so both numbers are reported.