I'm doing biogas production experiment in 1L flask. I follow water displacement method. And this experiment is conducted in normal room temperature. Current average day temp is around 36°C and night around 18-20°C. I kept 750ml working space and remaining headspace. But after 2 or 3 days, my flask is full of water filled. Even I used new pipe and airtight condition. This water accumulation starting during night time. Incase of day time it's not coming. Why it's happening? What to do for stopping this?
Bruno Peeters
The answer is simple: overnight cooling reducing the biogas volume and pressure.
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Abu Duguma Debele
Thermal Contraction at Night: During the day, the higher temperature (~36°C) increases gas pressure inside the flask. At night (~18-20°C), the temperature drops, causing the gas inside the flask to contract, it creates partial vacuum. This vacuum can suck water back into the flask from the displacement setup. No Issue in Daytime: Since the temperature is higher, gas expansion prevents water from entering to the flasks. Use a One-Way Valve: Install a one-way gas release valve to allow gas to escape but prevent water from backflowing. Increase Headspace: larger headspace or reducing working space to 700 mL can buffer pressure variations. Modify the Water Displacement Setup: Raise the water level in the displacement container so it’s not below the flask outlet. Add an additional small gas-collection chamber like a balloon or other before the water displacement system to act as a buffer.
The issue experiencing is likely due to temperature fluctuations between day and night.
How to Prevent Water Accumulation:
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