The net work of the cycle is defined by the difference between the turbine work and the pump work: If the pump work is neglected, the net work of the cycle reduces to: Then the thermal efficiency of this system is defined by the rate between the net work and heat transfer from the boiler: Air-Fuel ratio and Air Excess.
At The Airport Valet, we believe that you should only tip commensurate with the service you receive. That said, currently the average tip is $3.00 - $5.00 on both departure and arrival. However, daily our valetsâ tips do range from as low as $1.00 to as high as $30.00.
Here is the best I can conclude for the rules of the road, so to say, for how to tip when using valet parking in the U.S.: 1  Tipping upon drop-off of your car is totally optional and is not done by the majority of drivers.  A tip of $1 to $5 is the typical range, with $2-3 being most common.