The answer is no. The liver is a filter that filters out toxins from the blood but it does not produce body heat. Here is brief description of how the body produces heat by Dr. Swanson
http://www.madsci.org/posts/archives/1999-09/937368195.Gb.r.html
Sweaters do not produce heat themselves. They help to keep you warm by trapping the heat that your body produces. The material of the sweater acts as an insulator, preventing the heat from escaping and helping to maintain your body temperature.
The liver plays a role in regulating body temperature by producing heat as it metabolizes nutrients. It also helps to maintain a constant internal body temperature by controlling the breakdown of energy sources and regulating blood flow to different parts of the body.
Humans produce heat in order to keep warm. This is done by the body using its caloric reserves such as glucose and glycogen to make energy for the integumentary system to burn and thus heat up the body. If the body doesn't do this, it could undergo hypothermia and freeze to death.
The muscular system produces heat in the body through the process of muscle contractions. When muscles contract, they generate heat as a byproduct of the energy used during the contraction. This heat helps to regulate body temperature and keep the body warm.
Muscular activity produces heat in the body because when muscles contract and relax, they generate energy through chemical reactions. This energy is released as heat, which helps to maintain the body's temperature and keep it functioning properly.
They produce their own heat just as you do but instead of a coat and sweater they have blubber under their skin to help keep them warm. Being in water draws heat away from the body.
Endothermic animals rely on themselves to produce their own heat. Ectothermic animals, however, must rely on the sun to keep their body heat up.
The body keep a constant heat because f the blood running through the body. The body temperature does not change even if the temperatures of our surroundings change.
The body needs the liver survive because this is where toxins are excreted in the form of a bile. The liver has so many functions that is vital to human body. Keep in mind that the liver can be used as storage for blood until it is ready to be used.
It depends on the type of clothes. Normal clothes won't really "heat" you up, but they can keep you warm by trapping in heat. Your body is constantly producing heat, so by wearing clothes, you trap your body heat in, thus keeping you, and your clothes warmer. On the other hand, if you had clothes that produce heat themselves, such as electric blankets do, than you could say that they would heat you up.
Skin provides a waterproof barrier that maintains the body's moisture. It also provides insulation that helps keep body heat in the body.
Wet suits are supposed to keep the water out, and keep your body heat in, since the cold ocean will suck away a lot of your body heat, extemely quickly, so as to make the longest possible dive/swim time, wet suits keep your body heat in, and the water out.