'emit heat' is correct and can be used in written English.
You can use it to describe a situation in which heat is produced or released. For example, "The heater emits heat to warm the room."
Unfortunately, other road participants or artifacts emit heat as well (cars, heated buildings, etc).
Hawking drew on quantum theory to show that black holes should emit heat and eventually vanish.
Humans and other warm-blooded animals emit heat as infrared radiation.
And like Fan, some have succeeded in making materials that emit heat in the thermal window.
But his gesture — the audacity of his forgiveness — dominated South Africa's headlines for weeks, firing a controversy that continues to emit heat.
As humans emit heat-trapping gases, we expect to see changes to the Earth.
When humans burn fossil fuels, they emit heat-trapping gases into the atmosphere.
It is often considered the most important measure for predicting how much the Earth's temperature will increase as we emit heat-trapping gases like carbon dioxide.
Humanity's response must start with heading off as much unnecessary warming as possible by cutting dependence on fuels that emit heat-trapping greenhouse-gas emissions.
Prime Minister Atal Bihari Vajpayee said that developing countries like India could not afford to substitute cleaner but more expensive energy sources for the fossil fuels that emit heat-trapping gases.
