A heat exchanger or chiller may include a heat exchanger block having a first fluid channel for a coolant and a second fluid channel for a refrigerant, an expansion valve for controlling a mass flow rate of the refrigerant, and a connection flange having an inlet channel and an outlet channel for the refrigerant. The expansion valve may be designed as an electronic expansion valve. The inlet channel may be connected to the second fluid channel in a transition region of the inlet channel. The connection flange may have an insertion opening, which may communicate with the transition region of the inlet channel, and into which the expansion valve may be inserted such that the expansion valve may control the mass flow rate of the refrigerant in the transition region and evaporation of the refrigerant may first occur in the second fluid channel.