Thermal mass flow sensor vs. thermal flux sensor

[senmeis]

Hi,

What’s the difference between two similar sensors: thermal mass flow sensors (see attachment) and thermal flux sensors at https://vatell.com/index.php/thermogage. For me the former one is used to measure gas flow. What about the latter? Must there be gas for thermal flux sensors?

 

[jrmichler]

Thermal mass flow sensors measure mass flow, normally of a gas such as air. The output has units of mass per time, such as kg/sec.

Thermal flux sensors measure heat flow. The output has units of power per area, such as watts/cm$^2$. A good explanation is in the Thermogage User's Guide: https://vatell.com/images/Use of Thermogage v2.pdf. This is a link in the vatell.com link in the OP.

 

[senmeis]

There are two cases for thermal transfer: with or without gas.

With gas: Can thermal flux be calculated with flow measurement?
Without gas: Is this the case only in vacuum?