Using outdoor unit as heat recovery

[nike123]

I was wandering if it is possible to calculate how much energy we can recover from exhaust air in duct split system by directing exhaust ventilation (used air) to outdoor unit heat exchanger.
Since use of dedicated heat recovery heat exchanger is pretty expensive, i would like to quantify amount of energy recovered by that little trick.

For example (for heating operation):

Fujitsu duct system with nominal heating capacity of 8kW at 1100 m^3/h indoor air flow of wich is 20% fresh air. Indoor conditions are 21°C and 60% humidity.
Outdoor unit air flow is 2700m^3/h and outdoor temperature is -5°C with humidity of 45%.

Any help in how we can calculate what should be theoretically recovered with that introduction of 220m^3/h exaust air of 21°C and 60% in outside unit HE?

[mad fridgie]

Your limiting factor is still evaporating temp.
so the method
outdoor air flow - exhaust = ambient air flow (find energy level)
exhaust find energy level for the flow.
add the 2 levels together.
This should give you a new averaged air onto the evap (above your standard ambient)
What difference does the increase make to your SST, thus increasing your heat of rejection