Test bypass for a cooling apparatus, having a liquid vessel with a variable pressure level

A method for simulating an isothermal or non-isothermal heating load imposed by a consuming device (V) in a process medium (M) of a cooling apparatus (1), by means of a test bypass (2), wherein a flow connection between a “forward flow” (A) of the cooling apparatus (1) and a return flow (B) of the cooling apparatus (1) is provided, wherein the test bypass (2) is comprised of at least one regulating valve (CV1, CV2), a first heating means (H1) for introducing the isothermal heating load, a vessel (G), and a second heating means (H2) for introducing the non-isothermal load, wherein in the process the process medium (M) is passed from the “forward flow” (A) through the test bypass (2) to the return flow (B), wherein by means of the first heating means (H1) a predefined isothermal heating load is introduced into the process medium (M) and by means of the second heating means (H2) a predefined non-isothermal heating load is introduced into the process medium (M), in the test bypass (2), wherein by means of the at least one regulating valve (CV1, CV2) a process pressure (p4) is established in the vessel (G) into which the isothermal heating load is introduced, so that in the vessel (G) a constant level (LI4) of a liquid phase (F) of the process medium (M) is maintained, wherein in the test bypass (2) a state of the process medium (M) is measured at a point (Z1, Z2, Z6, Z7), and wherein, using the values of the state of the isothermal heating load and of the process pressure (p4) at the said point (Z1, Z2, Z6, Z7), the mass flow (m) of the process medium (M) at the point (Z1) is calculated.