Why does the temperature inside the pipe rise?
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There is an ACetylene pipeline with a diameter of DN900 (made of carbon steel), and both the inlet and outlet manual valves are closed. Why does the temperature inside the pipeline rise in summer? As thermal radiation increases, does the temperature inside the pipe keep rising continuously? Or will it reach a state of thermal equilibrium where it equals the external temperature?
The actual pipes heat up due to the thermal radiation from sunlight, and this heating is not caused by the ambient temperature; therefore, there is also a critical value for this increase in temperature. Since the intensity of sunlight and the duration of exposure per day are limited, this critical temperature is certainly much higher than the external temperature.
There are several reasons why the temperature inside pipes rises in summer: 1. High external ambient temperature: Higher temperatures in summer cause the temperature outside the pipes to increase. Since the pipeline is sealed and cannot exchange heat rapidly with the outside environment, the temperature inside the pipeline also rises as a result of the influence of the external temperature. 2. Heat absorption by the pipeline: The acetylene in the pipeline may be exposed to heat sources such as sunlight or thermal radiation from the surrounding environment during transportation, thereby absorbing heat and increasing in temperature. Especially under direct sunlight in summer, the pipes absorb more heat, leading to an increase in temperature. 3. Inefficient heat transfer: Carbon steel pipes have relatively poor heat transfer properties, resulting in slow heat transfer and a gradual increase in temperature within the pipes. The temperature inside the pipe will not keep rising indefinitely; it will reach a state of thermal equilibrium. When the inside of the pipe is affected by the external temperature and absorbs enough heat, its internal temperature gradually rises until it reaches a state of thermal equilibrium where it is equal to the external temperature. In this state, the temperature inside the pipe no longer rises further, but fluctuates according to changes in the external temperature. .
If not addressed in a timely manner, the temperature inside the pipe will become as high as the pipe’s temperature; moreover, due to the intensity of radiation, the pipe temperature is higher than the ambient temperature.