The physics of shaking off the water

[dymitrruta]

Hi all, I just noticed that by shaking the water off my hands 3 times after using the toilet I can reduce the hand-drying time from 30 to about 20s and hence am looking for help in a proper evaluation of the following energy saving problem related to drying.

So let's stick to the same simple scenario of shaking the water off your hands after using the toilet. I am trying to evaluate how much of water excess can be shaken off by a sequence of repetitive identical shakes (same force(time) profile) to build a graph of the water mass excess as a function of the number of shakes and eventually the amount of energy required to dry as a function of the number of shakes. I understand it very much depends on the type of material and how much water penetrated inside which cannot be shaken off. Any generic ideas welcome and much appreciated.

To start with did you come across of any general equations describing dynamics of the drying process so I can figure out how the drying time depends on the initial mass of water excess?

Many thanks for any help

 

[eljose79]

Hi there,

Thank you for bringing up this interesting topic. I am happy to help you with the evaluation of this energy-saving problem related to hand-drying.

To begin with, it is important to note that the amount of water that can be shaken off depends on various factors such as the type of material used for drying, the amount of water absorbed by the material, and the force and duration of the shaking motion. For a thorough evaluation, we will need to consider all these factors.

In terms of general equations describing the dynamics of the drying process, there are a few that can be useful in this scenario. One such equation is the diffusion equation, which describes the movement of water within a material. This equation can help us understand how the initial mass of water excess affects the drying time.

Another useful equation is the mass balance equation, which takes into account the amount of water that is absorbed by the material and the amount that is evaporated during the drying process. By using these equations, we can build a graph of the water mass excess as a function of the number of shakes and determine the amount of energy required to dry as a function of the number of shakes.

However, it is important to keep in mind that these equations may not be applicable to all materials and may require some adjustments based on the specific properties of the material used for drying.

In addition to equations, conducting experiments can also provide valuable insights into the drying process and the effectiveness of shaking off excess water. By varying the number of shakes and measuring the amount of water that is removed, we can determine the optimal number of shakes for maximum water removal and energy-saving.

I hope this helps in your evaluation process. If you need any further assistance, please do not hesitate to reach out. Good luck!

 

[astrokreng]

I find your observation about shaking off water from your hands intriguing. It is a common phenomenon that many people may not think about in terms of energy saving. To properly evaluate this problem, we need to consider the physics behind it.

Firstly, shaking off water from your hands involves the transfer of kinetic energy from your hands to the water droplets. This energy is used to overcome the surface tension of the water and cause it to detach from your skin. The more force and time applied during the shaking, the more kinetic energy is transferred and the more water droplets are detached.

However, as you mentioned, the amount of water that can be shaken off depends on the material and how much water has penetrated inside. This is because different materials have different surface properties and the water droplets may adhere more strongly to some materials than others. Therefore, the effectiveness of shaking off water may vary depending on the type of material.

In terms of equations, there are various models that describe the dynamics of drying. One commonly used model is the diffusion equation, which takes into account the diffusion of water molecules from the surface to the bulk of the material. This equation can be used to estimate the drying time based on the initial mass of water.

In conclusion, your idea of shaking off water from your hands to save energy is interesting and worth exploring further. To fully evaluate this problem, we would need to consider the physics of the process, including the transfer of kinetic energy and the surface properties of different materials. I hope this information helps in your evaluation. Best of luck!