Keeping cool during heatwaves.

If the wet bulb temperature exceeds about 35 deg C (severe heat wave conditions) then people could die within hours. One can drink cold drinks and use air conditioning and so on. Here is a device (see drawing below) to cool oneself with (or cool a group of people with). Anyone may manufacture this device and sell it, but please give me 0.5% (only half of 1%) of your profits if you manufacture and sell this device. I have not seen such a device anywhere else. For evaporative cooling calculations please contact me. I will also do simple radiation calculations related to this device. Theoretically the bottom wet surface could be cooled by wind to the wet bulb temperature (which will be below ambient air temperature unless the relative humidity is 100%). This cooler surface will radiate less infrared radiation. So people below will be air-cooled and also receive less heat radiation. Usually the relative humidity in heatwaves is low (perhaps 20%). The lower the relative humidity the more evaporative cooling you can get. Calculation: Say air temperature is 40 deg C and the relative humidity is 25% with atmospheric pressure of 100 kPa and the efficiency of evaporative cooling is 60% (in ideal conditions it would be 100%). Then the wet bulb temperature will be 23.8 deg C, the volumetric heat capacity of the air before cooling will be 1.124 kJ/(m^3.degC), the air will be cooled to 30.3 deg C and the mass of water evaporated to do the cooling will be 4.4 grams per cubic metre of air cooled to 30.3 deg C.

Here is a device (see drawing below) that can be fitted to roofs or made into a large "umbrella" shading device for the garden. Anyone may manufacture this device but please give me 0.5% (half of a percent only) of your profits if you manufacture and sell this device or similar device. I have not seen this device anywhere else. It could be substituted as a cheaper alternative to the device at the top of this group (three-sheet device). The basic principle depends on this: In the sun the top surface heats up a lot (perhaps to 20 deg C above the ambient air temperature). When the device is given a tilt air rises by natural convection between the two surfaces, cooling the device. The temperature of the upper surface is thus reduced and the upper surface of the device radiates less heat than if it were a single surface left in the sun. Since the device shades the ground you get less heat radiation from the ground and there will be an overall cooling effect for people under and near the device.

Rain to cool things off

Say your city is close to the sea and humidity over the sea has been increased by the use of shallow pools with dark bottoms (shallow pools heat up more in sunny weather than deep sea), floating spray generators that use wave motion and floats on arms that drive spray pumps, and so on. When the moist air from the sea moves onto land one needs a way to make the air rise so that it can cool and clouds can form. Generally air does not heat up much by radiation. Below about 10 km altitude air is warmed by contact with the hot ground, mixing, and if it has a lot of moisture in it is heated a little by water vapour absorbing infrared radiation from the ground.
But air can be heated far more efficiently and in massive volumes by using solar air heaters. This is because solar air heaters let air come into close contact with large hot surfaces.
http://www.builditsolar.com/Experimental/PopCanVsScreen/PopCanVsScreen.htm will explain this concept.
The solar air heater can be at least 50% efficient. This means that if 10 kWh per square metre of solar energy falls on it in a day, each square metre of the solar air heater can provide at least 5 kWh of energy to heat the air. It only takes about 1.2 kJ of energy to heat 1 cubic metre of air by 1 deg C (the volumetric heat capacity of air is about 1.2 kJ per cubic metre per deg C). In 1 kWh there are 3600 kJ so large volumes of air can be heated by each kWh of solar energy.
With solar air heaters on every roof of a city and in other places near the ground one can get the moist air from the sea to rise when there is a sea breeze (breeze from the sea onto the land). The air will rise and cool until it is at the same temperature as the surrounding air. If it rises far enough it will cool enough for clouds and rain to result.
For an imaginary city at latitude 25 degrees North you will have approximately this situation on sunny days:
1) On 1 January, 4.0 kWh of solar energy falls on one square metre of a horizontal surface on that day and 1518 cubic metres of air can be heated by 8 deg C by that one square metre (assuming 100% efficiency).
2) On 1 February, 4.8 kWh of solar energy falls on one square metre of a horizontal surface on that day and 1791 cubic metres of air can be heated by 8 deg C by that one square metre (assuming 100% efficiency).
Carrying on in this way I have drawn a graph of how many cubic metres of air can be heated by 8 deg C in a day by one square metre of solar air heater (assuming 100% efficiency).

So with solar air heaters huge volumes of air can be heated to high temperatures. The hot ground cannot do this nearly as well because the air only has contact at ground level.

Summary: Air can be made moist and the moist air can be heated efficiently by solar air heaters and made to rise so that rain results.

Wet Bulb Temperature and Heat Waves

THE OWNER OF THIS BLOG WILL NOT ACCEPT LIABILITY FOR ANY PROBLEMS OR MISTAKES THAT MIGHT ARISE FROM CALCULATIONS OR MATERIAL POSTED TO THIS PAGE:
You can get my easy to use wet bulb calculator program at http://gigsclerk.com/jobs/programming-technology/heat-wave-calculations/ for a dollar or two.
SEE https://www.facebook.com/Heat-Wave-533359286835145/ FOR CALCULATIONS ON WET BULB TEMPERATURES FOR YOUR AREA.
WET BULB CALCULATOR AT: http://www.srh.noaa.gov/epz/?n=wxcalc_rh Note that for coastal areas the pressure is usually around 760 mm of mercury. Up to an altitude of about 2 km the pressure difference does not make a big difference to calculations of wet bulb temperatures. At 2 km the wet bulb temperature might be up to 0.5 deg C or so less. You will have to find the relative humidity and temperature somewhere - perhaps from a weather report. After that you just need to enter the RH (relative humidity), the temperature and the pressure (perhaps 760 mm) into the calculator entry places.
Below are some of the messages I have been sending out to various sites:
The human body cannot cool itself below the wet bulb temperature by means of sweating. The wet bulb temperature is therefore an important indicator of the probability of heatstroke. This blog attempts to provide good information regarding the wet bulb temperature.
1) Keep relative humidity down. This means that you must not have too many people in a room as breathing and sweating, etc, can raise relative humidity.
2) Cool the walls, etc, with water from outside, etc. Radiation from walls, etc, increases the heat you receive.
3) You can cool yourself by drinking cold drinks, with ice, cold water and so on.
If you give me the temperature and relative humidity at your location I will do a wet bulb temperature calculation if there are not too many requests - see https://www.facebook.com/Heat-Wave-533359286835145/
TABLE YOU CAN USE TO DRAW YOUR OWN CONCLUSIONS:  https://en.wikipedia.org/wiki/Heat_wave 
gives a table with danger areas (relative humidity and temperature combinations)..
Example: T=36 deg C and RH (relative humidity)= 78. The wet bulb temperature is about 32.6 deg C. You are deep in the danger zone as a wet bulb temperature over about 30 deg C is dangerous if sustained
WORLD ECONOMY TO GET WORSE AS LABOR IS COMPROMISED BY GLOBAL WARMING?:
https://en.wikipedia.org/wiki/Wet-bulb_temperature states that, " A study by NOAA from 2013 concluded that heat stress will reduce labor capacity considerably under current emissions scenarios" as the world gets hotter and more humid. The site says, " A sustained wet-bulb temperature exceeding 35 °C (95 °F) is likely to be fatal even to fit and healthy people.." and "The wet-bulb temperature is the lowest temperature that can be reached under current ambient conditions by the evaporation of water only " So if the temperature is 37 degrees Celsius and the relative humidity is 86% we have a wet bulb temperature of about 35 degrees Celsius (my calculations). Already in Port Elizabeth in March we have an average relative humidity of 81%. What about Durban and other humid places?
Talking about the heat wave in Pakistan that killed hundreds of people the Internet article "Wet Bulb Temperatures 35 C by Robertscribbler" says that wet bulb climbed into a dangerous range of 30 to 33 degrees Celsius. The wet bulb temperature is the coldest one can get via evaporation of water. The human body has an average temperature of 37 degrees Centigrade and cools itself by means of evaporation If the wet bulb temperature is 35 degrees Celsius or above the body cannot use evaporation to cool sweat below 35 deg C. This means that effectively the body cannot cool itself down and the person will probably die after a while. There is nowhere on Earth where the wet bulb temperature is as high as 35 deg C, but the article says in the Pacific record global atmospheric and ocean heat is pushing maximum sea surface temperatures into the lower 30s (typically between 30 and 31 degrees Celsius). THIS IS DANGEROUSLY CLOSE TO 35 deg C. You can calculate wet bulb temperatures by using a calculator on the internet (they do not always agree precisely with each other, but you should get an answer correct within 0.5 deg C or so). AN IDEA OF MINE: Pump seawater (or use the tide) into large shallow ponds and let it evaporate forming large salt crusts with high albedo that will reflect solar energy back into space. Do this on the perimeters of continents.https://en.wikipedia.org/wiki/Wet-bulb_temperature confirms that,
"The wet-bulb temperature is the lowest temperature that can be reached under current ambient conditions by the evaporation of water only." What happens if the temperature is 37 deg C and the relative humidity is 85%. My program SWetbulb shows you could be in trouble.
You can download my program SWFridge that calculates the wet bulb temperature at groups.yahoo.com/neo/groups/wetbulb/info
LEAVING A DOG IN A CAR IN HOT CONDITIONS: Hyperthermia in dogs. The wet bulb temperature is the coldest one can get via evaporation of water. https://en.wikipedia.org/wiki/Wet-bulb_temperature confirms that, "The wet-bulb temperature is the lowest temperature that can be reached under current ambient conditions by the evaporation of water only. A dog cools itself by panting and therefore evaporation. IF YOU LEAVE A DOG IN A CAR: Evaporation occurs as the dog pants to cool itself, so the relative humidity goes up, so the wet bulb temperature goes up, so the dog could become overheated and possibly die. The reason is that evaporation cannot cool the dogs mouth, etc, below the wet bulb temperature and the wet bulb temperature increases as the relative humidity increases.
COULD NEWSPAPERS , etc, INCLUDE WET BULB TEMPERATURES IN WEATHER REPORTS?
Wet bulb temperatures again (sorry, but it seems things are getting risky re heat waves). On 6 June 2015 THE NEW YORK TIMES reported the following:
(Beginning of report notes)
1) The wet-bulb temperature is not typically reported. While dangerous levels depend on a person’s activity level and clothing, wet-bulb temperature offers a stark measure of risk in a warming world that will experience more extreme combinations of both heat and humidity.
2) Statistical analyses and climate modeling indicate that the 2010 Russian heat wave was about five times more likely to have occurred in 2010 than it would have been in the cooler 1960s.
3) But sweating, which helps keep the core body temperature constant, becomes increasingly ineffective in increasingly humid air, and it can never cool the skin to below the wet-bulb temperature (end of report notes).
Personally, I think it is time to take serious note of wet bulb temperatures. Hopefully newspapers will start publishing them.
See http://www.nytimes.com/…/the-deadly-combination-of-heat-and…