Important factors of data center energy efficiency: latent heat and sensible heat

Talking about the PUE value of data centers has always been a topic of concern to many data center managers. Everyone knows that data centers are energy-intensive industries. Managing energy efficiency is equivalent to controlling the expenditure costs of data centers, but how can we effectively control the energy consumption of data centers?

Speaking of the main factors that affect the energy consumption of data centers, it must be heat. Data centers have a large number of IT equipment running, which will emit a lot of heat. This heat needs to be offset by the medium carrying the same amount of cold. So first of all, let's understand what heat is? What are the types of heat?

The heat that an object absorbs or releases when its temperature rises or falls without changing its original phase during heating or cooling is called "sensible heat". It can make people feel obvious changes in temperature and can usually be measured with a thermometer. (For example, the heat absorbed by water when the temperature rises from 20°C to 80°C is called sensible heat. Latent heat: The heat absorbed or released when a substance undergoes a phase change (physical state change) without changing its temperature is called "latent heat".

When a substance changes from a low energy state to a high energy state, it absorbs latent heat, and when it changes from a low energy state to a high energy state, it releases latent heat. For example, when a liquid boils, part of the latent heat absorbed is used to overcome the attraction between molecules, and the other part is used to do work against the atmospheric pressure during the expansion process. Heat of fusion, heat of vaporization, and heat of sublimation are all latent heat. The value of latent heat is often expressed as the amount of heat absorbed or released per unit mass of the substance or per mole of the substance during the phase change.

Sensible Heat Ratio (SHR)

Heat load is divided into two parts: sensible heat and latent heat. The removal or increase of sensible heat will cause a corresponding change in the temperature of the dry bulb thermometer. Latent heat is related to the increase or decrease of air humidity. The total cooling capacity of the air conditioning system is the sum of the capacity to regulate and handle latent heat and sensible heat. The sensible heat ratio is the proportion of sensible cooling capacity in the total cooling capacity. That is, sensible heat ratio (SHR) = sensible cooling capacity / total cooling capacity.