According to the heat function definition any H = constant " heatline " is locally parallel to the direction of net energy flow through the convection field.
3.
The latent heat accumulator is separate to the Residual Heat function ( activated by a button labelled " REST " ), which allows the demister and cabin heater to use the heat of an engine that has recently been turned off ( using an electric pump to push hot coolant through the heater core ).