Making a snow and Inflating a bicycle tire (chapter.6) By Group No:1 Wisawa M. 5435121 Santi P. 5516847 Nuthapat S. 5532013 Antonio L. 5538435

What is snow? Snow cover is a part of the cryosphere, which traces its origins to the Greek word kryos for frost. Snow is precipitation in the form of ice crystals. It originates in clouds when temperatures are below the freezing point (0 degrees Celsius, or 32 degrees Fahrenheit), when water vapor in the atmosphere condenses directly into ice without going through the liquid stage. Once an ice crystal has formed, it absorbs and freezes additional water vapor from the surrounding air, growing into a snow crystal or snow pellet, which then falls to Earth.

Two of the Most Important Variables in Making Snow Temperature and Humidity; Both of them must be low enough for snowmaking. Water Temperature; Water must be colder than the outside. Ex. Outside 9 C, water must be lower than -1 C

How does it work? Ambient Temperature; outside must be cold at least freezing point Evaporation; The second factor is heat loss through evaporation. Surface Area The third way we cool the water is by increasing the surface area of the drop.

The Science of Snow Making

Heat Exchange Process  Snow making is a heat exchange process. Heat is removed from snowmaking water by evaporative and convective cooling and released into the surrounding environment.

Wet Bulb Temperature  The temperature of a water droplet exiting a snow gun is typically between 1 C and 6 C. Once a water droplet passes the nozzle and is released into the air, its temperature falls rapidly due to expansive and convective cooling and evaporative effects.

Nucleation Temperature  Once the wet bulb temperature is know, there must be a way to predict whether water droplets will actually freeze at that temperature. Ice is the result of a liquid (water) becoming a solid (ice) by an event called nucleation. A water droplet must first reach its nucleation temperature to freeze. 

Liquid form Solid form (hexagonal array)

Inflating Bicycle Tire

INTRODUCTION Thermodynamics is the scientific study of the interconversion of heat and other kinds of energy When a tire is full of air, it is said to be inflated. When a tire has less air in it then it needs to operate it is said to be deflated. U = q + w

WHY DOES THE BICYCLE TIRE GET HOT WHEN INFLATED? U = q + w Work is done to the gas in the tire, so the value of w is positive and q = 0 The increase of w leads to the increase of  w increase = temperature increase

If the gas is thermally isolated from the surroundings, then the process is said to occur adiabatically (adiabatic change) First Law becomes ΔU = 0 + w Interaction form between particles with the concurrent release of energy

Adiabatic Adiabatic is the change of energy When a gas expands, it does work on the surroundings compression of a gas to a smaller volume similarly requires that the surroundings perform work on the gas In an adiabatic change, q = 0, so the First Law becomes ΔU = 0 + w

Since the temperature of the gas changes with its internal energy it follows that adiabatic compression of a gas will cause it to warm up adiabatic expansion will result in cooling