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Hot Air Balloon - Lifting Force

source : engineeringtoolbox.com

Hot Air Balloon – Lifting Force

Hot Air Lifting Force

The lifting force from a hot air balloon depends on the density difference between balloon air and surrounding air, and the balloon volume. The lifting force can be calculated as

 Fl = V (ρc – ρh) ag                         (1)

where

Fl = lifting force (N, lbf)

V = balloon volume (m3, ft3)

ρc = density cold surrounding air (kg/m3, slugs/ft3)

ρh = density hot balloon air (kg/m3, slugs/ft3)

ag = acceleration of gravity (9.81 m/s2, 32.174 ft/s2)

Example – Lifting Force created by a Hot Air Balloon

A hot air balloon with volume 10 m3 (353 ft3) is heated to 100 oC (212 oF).   The temperature of the surrounding air is 20 oC (68 oF). The air density at temperature 100 oC is 0.946 kg/m3 (0.00184 slugs/ft3) and the air density at temperature 20 oC is 1.205 kg/m3 (0.00234 slugs/ft3).

The lifting force can be calculated as

Fl = (10 m3) [(1.205 kg/m3) – (0.946 kg/m3)] (9.81 m/s2)

  = 25.4 N

Weight – or gravity force – can be calculated as

Fg = m ag                       (2)

where

Fg = weight – gravity force (N, lbf)

m = mass (kg, slugs)

Since lifting force of a flying air balloon equals weight (Fl = Fg) – the lifted mass can be expressed by combining (1) and (2) to

m = Fl / ag

   = (25.4 N) / (9.81 m/s2)

   = 2.6 kg

The calculation of lifting force can be done in Imperial units as

Fl = (353 ft3) [(0.00234 slugs/ft3) – (0.00184 slugs/ft3)] (32.174 ft/s2)

   = 5.7 lbf

Hot Air Balloon – Specific Lifting Force

Specific lifting force (force per unit air volume) created by an hot air balloon – balloon temperature vs. surrounded air temperature – are indicated in the charts below.

SI – units 

Imperial Units

Example – Specific Lifting Force from a Hot Air Balloon

If the balloon temperature is 60 oC and the surrounded temperature is -20 oC – the chart indicates a specific lifting force

3.3 N/m3

Hot Air Balloon Lifting Force Calculator

This calculator can be used to calculate the lifting force of a volume with lower density than surrounding air.

balloon volume (m3)

balloon volume density (kg/m3)

surrounding air density (kg/m3)

Hot Air Baloon Problem | Physics Forums

Hot Air Baloon Problem | Physics Forums – A hot-air balloon achieves its buoyant lift by heating the air inside the balloon, which makes it less dense than the air outside. Suppose the volume of a balloon is 1820 m3 and the required lift is 2983 N (weight of equipment and passenger). Calculate the temperature of the air inside the balloon which will produce the desired lift.With this in mind we can calculate the density of the heated air at a given temperature, using the Ideal gas law, as follows: P = ρRT Where: P is the absolute pressure of the gas, in Pa ρ is the density of the gas, in kg/m 3 R is the gas constant, in Joules/kg.K T is the absolute temperature of the gas, in Kelvins (K) Now, Normal atmosphericHot air balloons float in the air because of the difference in density between cold and hot air. In this problem, you will estimate the minimum temperature the gas inside the balloon needs to be, for it to take off. To do this, use the following variables and make these assumptions: The combined weight of the pilot basket together with that of the balloon fabric and other equipment is W. The

Hot Air Balloon Physics – Hot air balloons float in the air because of the difference in density between cold and hot air. In this problem, you will estimate the minimum temperature the gas inside the balloon needs to be, for it to take off. To do this, use the following variables and make these assumptions: The combined weight of the pilot basket together with that ofHot air balloons work because hot air rises. By heating the air inside the balloon with the burner, it becomes lighter than the cooler air on the outside. This causes the balloon to float upwards, as if it were in water. Obviously, if the air is allowed to cools, the balloon begins to slowly come down.Hot air balloons float in the air because of the difference in density between cold and hot air. In this problem, you will estimate the minimum temperature the gas inside the balloon needs to be, for it to take off. To do this, Math. A hot air balloon descends at a rate of 320 feet per minute for 3 minutes.

Hot Air Balloon Physics

Hot air balloons float in the air because of the – Hot air balloons float in the air because of the difference in density between cold and hot air. In this problem, you will estimate the minimum temperature the gas inside the balloon needs to be, for it to take off. To do this, Science Halp. 1 When the air under the envelope is heated, the balloon lifts.A recreational (open) hot air balloon (i.e., Pinside is approximately Poutside) has a volume of 2267 m3 when fully inflated. The total weight of the balloon, basket, ballast and pilot is 1989.4 N (448 lbs). By how much must the density of the air in the balloon be smaller than that of the surrounding atmosphere in order to keep the balloon floating level near the ground?The temperature is different for the two cases. Both inside and outside the balloon, the pressure is assumed to be ## P ##=1 atm. The pressure may be slightly higher than this inside the balloon, but to a good approximation, in a hot air balloon, the pressure is ## P ##= 1 atm.

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density | MrReid.org