Mass of Steam Supplied during Wort Boiling Flashcards
(17 cards)
What is one means of estimating evaporation?
Measuring the mass of steam supplied to the kettle
This method provides an estimate rather than a direct measurement.
What happens to steam as it gives up its latent heat?
It condenses into a liquid
This heat is then transferred to the wort.
What is the relationship between the mass of steam supplied and the heat supplied to the wort?
The mass of steam supplied is proportional to the heat supplied to the wort
This is also proportional to the amount of water evaporated from the wort.
What assumptions are made when measuring steam to estimate evaporation?
- All steam supplied is used to heat the wort
- No heat losses due to leaks or faulty steam traps
What are steam traps?
Devices fitted in the steam line after the calandria/jacket that allow only liquid to flow back to the boiler feed tank
If faulty, steam can flow back without heating the wort.
How can kettle design affect evaporation rates?
Some designs achieve more evaporation per unit of energy by providing a larger surface area of wort exposed to the atmosphere
What is the purpose of measuring the mass flowrate of steam?
To estimate the rate of evaporation and control boiling
How do breweries determine when the boil is complete?
Using the total mass of steam supplied
This is often checked against changes in gravity for accuracy.
What is the equation to calculate the required mass of steam?
Required mass of steam (kg) = (volume (hL) × 1.017 × target % evaporation × 65) / boil time (min)
What do the factors 1.017 and 65 account for in the steam calculation?
- 1.017 accounts for the change in the volume of wort between 75°C to 100°C
- 65 accounts for radiant heat losses
How much steam is required to evaporate 1 kg of water?
Just over 1 kg of steam
This is because the energy to evaporate the water comes from the steam as it condenses.
What happens when the heating surface in the boiling system becomes fouled?
The boil will take longer due to reduced heat transfer into the wort
What can be used in small breweries to monitor boil time?
Metering the kW of electricity supplied to the kettle
What is the specified start of boil gravity in the example?
10.2°P
What is the specified end of boil gravity in the example?
10.8°P
What could cause a discrepancy in the end of boil gravity?
Possible issues with the brewing process
For example, if the actual end of boil gravity is lower than expected.
If the start of boil gravity was 10.0°P, what could this indicate?
Potential issues with the wort preparation or measurement inaccuracies
