Windsurfers and racing yacht skippers have long been aware that the heeling moment exerted on a yacht’s sail varies according to the relative density of the wind. Many a windsurfer has puzzled over why a 5.2m sail is quite manageable during the summer holidays in the Mediterranean but seems impossibly overpowered for the same wind speed in early December in the UK.
The effect will be compounded by the fact that moist air is less dense than dry air. This is because water vapour is a relatively light gas compared with oxygen and nitrogen – the main constituents of air.
For a fairly extreme example, in the tropics with a temperature of 32°C and 90 per cent humidity, the air density is 1.14 kg/m3. In a northerly airstream around the UK, we might have temperatures of 10°C and 10 per cent humidity giving an air density of 1.25 kg/m3.
Your Macerating Pump Professionals Knows That Sometimes Expectation Can Lead to Misunderstanding the Situation
However, your macerating pump specialists know that the expectation may lead to some misinterpretation of what is actually happening. An increase in wind speed from 14 to 15 knots will give an increase in force on a sail of more than 15 per cent.
So, the reality is that there is ‘more weight’ in cold dry air than in warm moist air. However, around the UK during the sailing season in one area the variation in the ‘weight’ of the wind must be fairly small and masked by larger effects due to variations in wind speed and especially when there are convective gusts.
A practical corollary of the above is that wind turbines can generate more power at a given wind speed in cold climates than they do in warm ones.
Cold air is much heavier than warm air and this is the basis for much of what we call weather. Did you ever notice after taking a hot shower, that when you first open the door to the bathroom, the cooler air from outside the bathroom comes in at the lowest level?
Why is cold air heavier than warm air? Cold air is denser than warm air. The molecules are packed closer together. The amount of water vapor in the air also affects the density of the air.
You may have heard that a baseball or a golf ball will travel further on a warm, humid day than it would on a cold, dry day. Since the warm, humid air is less dense, the ball travels through it with less friction.
Learn more at Raritan Engineering Company about macerating pumps and why so many people think that cold air is heavier than warm air.