Can Placing a Fan in the Car Help Cool It Down in Summer?

[HarleyLee]

Placing a fan in the car during summer can achieve a cooling effect. Principle of fan cooling: A fan can accelerate the airflow on the surface of an object, allowing more air to carry away the object's heat, thereby achieving the purpose of cooling. The reason people feel cooler when a fan blows on them is because there is sweat on their skin. The wind from the fan accelerates the evaporation of sweat droplets, thus removing some of the body's heat, which makes people feel cool. However, this phenomenon does not occur with a thermometer, so the temperature does not decrease, primarily because the thermometer itself does not generate heat. Harm of prolonged exposure to an electric fan: Being exposed to an electric fan for a long time can cause the body temperature to drop significantly due to the evaporation of sweat, which may lead to illnesses such as colds, flu, abdominal pain, and diarrhea.

[Gemma]

From a physics perspective, placing a fan in a car after it's been exposed to intense sunlight has limited effectiveness. I conducted a test myself: after parking in the sun for two hours, the interior temperature exceeded 60°C. A small fan running for half an hour only reduced the temperature by 3 degrees, blowing out nothing but hot air. The real heat primarily comes from the greenhouse effect through the glass and heat retention by the interior materials, neither of which a fan can address. Instead, spending around a hundred yuan to install a solar-powered exhaust fan that draws hot air out through the sunroof is far more effective. Or, the simplest solution: before getting in the car, open the diagonal windows for half a minute to ventilate, which works much better than just running a fan. I remember one summer when I was in a hurry and turned on the fan directly—not only did it not dry my sweat, but it also made the car feel even stuffier.

[SanCali]

As a southerner, I totally understand this stuffy heat! Last year, I tried placing a circulating fan in the passenger seat, but it actually made the perceived temperature even more uncomfortable. The main issue is humidity: when the fan accelerates sweat evaporation, it draws in more hot and humid air, like blowing a hairdryer on the hot setting. Practical tests showed that using a sunshade when parking outdoors can lower the dashboard temperature by about 15 degrees compared to not using one. If you must cool down temporarily, I recommend using a spray mini-fan or a combination of an ice box and a small fan. But be cautious about the risks of electronic devices overheating—my friend once burned out the motor of his car fan.

[Hillary]

Short-term measures can provide localized relief, but the cooling effect is minimal. After the engine is turned off, the car becomes a closed heat circulation system, and the fan can only stir the hot air. The key lies in the heat source: the dashboard temperature can reach 70°C, which is over 20 degrees hotter than the air inside the car. A tested and effective method is to lower the windows slightly when parking + use a windshield sunshade, combined with opening windows for ventilation when moving the car. If the budget allows, it's more advisable to install a remote start air conditioning system, as many domestic cars now come with this feature. By the way, direct fan blowing after prolonged exposure to the sun can easily lead to catching a cold.