HEAT PUMP HEATER

A heat pump heater for an air conditioning system of a motor vehicle may include a first tube row and a second tube row each including a plurality of flat tubes arranged spaced apart from one another. The first and second tube row may be arranged in parallel to form a tube block. At least some flat tubes of the first tube row may lead into an inlet pipe and at least some flat tubes of the second tube row may lead into an outlet pipe. A refrigerant may be flowable from the inlet pipe via the first tube row and to the outlet pipe via the second tube row. The inlet pipe and the outlet pipe may be fluidically connected to one another via at least one bypass duct such that a liquid phase of the refrigerant is flowable out of the inlet pipe into the outlet pipe.