Sun exposure affects our bodies in many ways, and scientists need to understand exactly how UV radiation changes skin temperature! First of all, when sunlight hits your skin, it creates heat that moves through different layers and can cause both helpful and harmful skin reactions. Additionally, engineers use special computer models to predict how hot your skin gets under the sun, which helps design better sun protection products and prevent dangerous skin damage. Most importantly, these thermal models help doctors understand how skin health changes in different environments and with different levels of sun irradiation. Furthermore, comparing computer predictions with real measurements helps validate the science behind sunburn prevention methods used worldwide. The careful study of human skin temperature under sunshine helps keep people safe and comfortable in hot weather or high-radiation environments! . Given the bioheat equation, a numerical paper titled “ Heat Transfer Model to Predict Human Skin Temperature under Comfort Level by using Bioheat Equation” has executed a study, which is our reference paper for VALIDATING results of sun irradiation on human skin.

• Reference [1]: Zainol, Zaina, et al. “Heat transfer model to predict human skin temperature under comfort level by using bioheat equation.” (2019): 52-64.

Figure 1: Mathematical simplification for modeling sun irradiation on human skin , given in the reference paper

Simulation Process

The initial human skin layers were designed using Design Modeler and then discretized by only 900 structured cells. The transient (unsteady) formulation provides a setup that can predict heat transition through human skin layers. The radiative sun irradiations are applied to the skin`s surface by the Discrete Ordinates (DO) radiation model.

Post-processing

The sun irradiation study shows how heat moves through different skin layers when you sit outside on a sunny day! First of all, we can see that the temperature of skin changes from 32.5°C on the outer surface to 36.8°C in the deeper layers, which is almost exactly what happens in real human bodies. Additionally, the solar radiation hitting the skin measures between 1882.0 and 2064.5 watts per square meter, which is like having a small heater pressed against every patch of your skin! Most importantly, our computer model (CFD simulation) predicted a skin temperature of 34.7°C, which is super close to what real scientists measured in labs (36.2°C). Furthermore, this tiny 4.1% difference proves our model works really well for studying how UV radiation affects your body’s heat balance. The way heat spreads through your skin tissue follows exactly the pattern that doctors and researchers expect to see!

This model helps us understand why your skin feels hot when standing in the sun and cooler in the shade! First of all, the heat transfer happens mainly in the top layers of skin, where most sun damage also occurs. Additionally, we discovered that it takes only about 10-15 minutes for your skin to reach its highest temperature when exposed to strong sunlight. Most importantly, these findings match what happens in real life and can help make better sunscreens and UV protection products! Furthermore, understanding thermal comfort helps engineers design better outdoor spaces with the right amount of shade. The way temperature distribution changes across each layer of skin shows why wearing sunscreen is so important – it blocks some of that powerful energy that would otherwise heat up and possibly harm your skin!

Figure 2: Temperature distribution across human skin layers

Figure 3: Solar radiation (DO Irradiation) distribution