Máy lạnh hoạt động theo chu trình Carnot làm lạnh cǎn phòng đến nhiệt độ 17^circ C và tỏa nhiệt ra ngoài ở nhiệt độ 37^circ C . Tính hệ số làm lạnh của máy. A. -15,5 B. 1,45. C. 14,5. D. 15,5.

The Coefficient of Performance (COP) is a measure of performance for cooling and heating machines. It is defined as the ratio of desired output to the required input. For refrigeration or air conditioning systems, COP is the ratio of the rate of heat removal to the rate of energy input. For a Carnot refrigerator, the owner wishes to find out the cooling effect of the machine (the desired output), so the formula for COPcooloing Calculation, also known as Carnot COP is Tcool / (Thot-Tcold), where Tcool is the temperature to which the cold space is to be maintained and Thot is the high temperature reservoir with which the refrigerator discharges heat. The temperatures must be converted to Kelvin from degree celsius by adding 273. So for Tcool, we’ll add 273 to 17 degrees Celsius to get 290K. For Thot, we add 273 to 37 degrees Celsius to get 310K. Using the formula, we divide 290K by the difference between 310K and 290k which gives us 17.