What you are looking at right now is a curve for an Air to Air Heat Pump.

• Todb is the outdoor air temperature, which is the temperature of the air entering the outdoor coil (condenser in cooling mode, evaporator in heating mode).
• Tdb is the dry-bulb temperature of the air reaching the indoor coil (evaporator in cooling mode, condenser in heating mode).

For an Air-To-Water heat pump, maybe you could look at using a biquadratic curve such as this one:

Where:

• Ta = Evaporator inlet air temperature (either dry-bulb or wet bulb)
• Tw = Condenser inlet water temperature

Are you familiar with EnergyPlus? In the Example files, there is one called "HeatPumpWaterHeater.idf" that you should take a look at in particular (and a few others that have air cooled chillers)

What you are looking at right now is a curve for an Air to Air Heat Pump.

• Todb is the outdoor air temperature, which is the temperature of the air entering the outdoor coil (condenser in cooling mode, evaporator in heating mode).
• Tdb is the temperature of the air reaching the indoor coil (evaporator in cooling mode, condenser in heating mode).

What you are looking at right now is a curve for an Air to Air Heat Pump.

• Todb is the outdoor air temperature, which is the temperature of the air entering the outdoor coil (condenser in cooling mode, evaporator in heating mode).
• mode). Tdb is the temperature of the air reaching the indoor coil (evaporator in cooling mode, condenser in heating mode).