AC load absolutely varies with blower speed.
On most modern vehicles (like your CRV, without an orifice tube) the amount of liquid refrigerant metered into the evaporator is controled by a Thermal Expansion Valve, or "TXV". The TXV takes it's cue from the temperature of the evaporator core.
Here's a great desciption of (stationary) TXV operation
Critical here is the pressure balance operation of the TXV:
TXV Pressure Balance EquationTXV
P1+P4 = P2+P3
P1 = Bulb Pressure (Opening Force)
P2 = Evaporator Pressure (Closing Force)
P3 = Superheat Spring Pressure (Closing Force)
P4 = Liquid Pressure (Opening Force)
Note that the "bulb" (P1) is a sealed system, with a refrigerant inside, but unrelated to the refrigerant in the rest of the system. The bulb is physically buried in the evaporator core, and reads the temperature of the core by thermal conductivity. The pressure inside the bulb rises as the core temperature increases. This pressure cooperates with the head pressure to open the TXV and allow more refrigerant into the evaoprator core.
Now, the temperature of the evaporator core rises proportionately as the temperature and flow of "hot" air across it. It's not completely linear, as the efficiency of any heat exchanger is usually flat only across a narrow range of secondary flow. Fast moving air just doesn't maintain enough "contact time" for heat exchange. Nevertheless, the overall amount of work done by the system is ultimately dictated by the temperature and flow across two heat exchangers, the evaporator and the condensor.
Another useful purpose of the TXV is to prevent evaporator icing, which has a runaway effect if left unchecked. Ice crystals block the airflow, less heat is absorbed into the evaporator, more ice is formed, less airflow ...
The TXV bulb will radically drop in pressure as the evap temperature approaches freezing, and cause the TXV to completely shut off liquid refrigerant flow into the evaporator to prevent this condition.
While I agree that most compressors (like your '04 CRV) are basically on/off devices, this does not describe the entire picture of energy, work, and heat conservation. Also, I am NOT suggesting that the TXV is used for cabin temperature control. Other posters have correctly mentioned this is almost always accomplished with the "blend door" mixing in heat with the post evaporator flow.
In fact, some compressors [very expensive German ones] use a variable swash plate that can change the stroke (displacement) of the compressor on the fly. Controlled by the ECU usually, by a multitude of inputs such as engine RPM, AC load, road speed (condensor airflow), emissions, idle, engine load (WOT?), and fuel efficiency goals. In this case, the compressor changes how much "compressinating" it needs based on load control from the ECU. These systems, while uber-trick, probably cost more than their efficiency gains.
In any case:
- High hot evaporator airflow raises evaporator temperature
- Evaporator temperature expands the magic juice in the TXV bulb
- TXV bulb pressure opens liquid refrigerant flow into the evaporator
- Refrigerant expasion in the evaoprator removes heat from the airflow