Explain why a room can be warmed by leaving open the door of an oven but cannot be cooled by leaving open the door of a kitchen refrigerator.

In an oven the electrical energy is converted into heat engine. The entropy of the system increases as it is heated. So the temperature of the surrounding will increase. Thus a room can be warmed by leaving open the door of an oven.
A kitchen refrigerator is a device which is used to keep bodies at temperature lower than the surroundings. It is based upon the thermodynamic principle that cooling is caused by evaporation. By leaving the door of a kitchen refrigerator, the recycled heat will enter to the refrigerator and will come out from the refrigerator to the room again like a remove of water by using water pump. The entropy of the system increases when the refrigerator is on. So the temperature of the surrounding will increase. Therefore the room cannot be cooled by leaving open the door of a kitchen refrigerator. The room can be cooled by leaving open the door of a kitchen refrigerator but keeping the refrigerator is off