Chemical engineering tip: Latent heat vs. sensible heat. Please share your insights~~~
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Hello everyone: As a newcomer, I’d like to share two terms from the field of chemistry. Please give me your guidance! ! The heat absorbed or released by a substance with latent heat when it undergoes a phase change (a change in state) is called \"latent heat\". A substance absorbs latent heat when it transitions from a low-energy state to a high-energy state, and releases latent heat in the reverse direction. For example, when a liquid boils, part of the latent heat absorbed is used to overcome the attractive forces between molecules, while another part is used to do work against atmospheric pressure during expansion. Enthalpy of fusion, enthalpy of vaporization, and enthalpy of sublimation are all latent heats. The amount of latent heat is often expressed as the heat absorbed or released per unit mass of a substance, or per mole of a substance during phase change. In a first-order phase transition, heat is absorbed or released accompanied by a change in volume, but the temperature of the system remains constant. The heat absorbed or released is called “latent heat of phase change”. The latent heat of phase change is related to the temperature at which the phase change occurs; for a given mass of a substance, the latent heat of phase change at a specific temperature remains constant. If U1 and U2 represent the internal energy per unit mass in phase 1 and phase 2, respectively, and V1 and V2 represent the volume per unit mass in phase 1 and phase 2, respectively, then the latent heat of phase transition absorbed per unit mass of material as it transitions from phase 1 to phase 2 can be expressed by the following formula: l = (U2 – U1) + P(V2 – V1) = h2 – h1. Here, P is the external pressure acting on the system, and h1 and h2 are the enthalpies per unit mass in phase 1 and phase 2, respectively. The phase transition latent heat formula in the above equation shows that the phase transition latent heat l consists of two parts: the internal latent heat (U2-U1) and the external latent heat [P(V2-V1)]. Sensible heat is the heat that must be absorbed or released by an object during heating or cooling, resulting in an increase or decrease in temperature without a change in its phase state. This is what is referred to as “sensible heat”. It can cause people to experience a noticeable change in temperature, which can usually be measured with a thermometer. (The heat absorbed when raising water from 20°C to 80°C is called sensible heat.) ）
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Actually, I don’t think there’s anything wrong with this post. . . Indeed, it’s easy to find such knowledge points. But not many people must truly understand the actual definitions of both. High-tech content is certainly great, but if our forum could have more such little facts and tips, I think Haichuan would become a real encyclopedia! ! Why go through all this trouble over a small issue? We have it in Haichuan! I have only one goal: to enrich HaiChuan for all of us! Do not refrain from doing good just because it seems small! ! :victory:
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