You work in an enzyme factory where a very precise temperature of $45\mathrm{.}0$ C is required at one stage of the process. In that situation, you cannot use a thermometer, but you do have a heat exchanger and an accurate pressure gauge. How do you arrange the most accurate temperature of $45\mathrm{.}0$ degrees on the other side of the heat exchanger? You can assume that the metal separating the different sides of the heat exchanger does not resist heat transfer at all. Briefly describe the arrangement with perhaps a simple diagram.