Who knows how to determine the heat loss in the ammonia synthesis shift unit?
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When calculating the heat balance for a certain section of the furnace, it’s not possible to determine the heat loss. The data provides an assumed value for heat loss, and as long as the temperature difference obtained from subsequent calculations matches that of the original design, it’s fine. I don’t know how to determine this value or how to estimate the heat loss; is there any basis for doing so? Does anyone know? Please help me, thank you
I’m afraid there’s no scientific basis for this. The original poster can first carry out a calculation using the assumed values from the available data; generally, there won’t be any significant discrepancies in the final results. Alternatively, it’s also possible to determine the heat loss based on the temperature drop.
I used values that were similar to those in the book; the resulting temperature difference was 10 degrees. I then adjusted the values again, and in the end the difference between the calculated value and the actual temperature difference was around 1 degree. What do you think? It only reduces the heat loss, but it seems to me like the values are being adjusted arbitrarily, which gives it a strange feel
Generally speaking, a temperature drop of 5 degrees or less due to heat loss can be considered acceptable. After completing your calculations, please remember to share them in the resource section. Looking forward to it... It is recommended that you create a dedicated thread in the discussion forum and post each step of your calculations there, so that everyone can discuss them together.
Okay, once I’ve finished the calculations, I’ll send my results so everyone can take a look. Today I went to see the teacher, and she said that for heat loss, we should first use the ratios given in the reference materials to make preliminary calculations, in order to see if the resulting temperature difference is appropriate
Find a book on ammonia synthesis and do some calculations to see if it’s suitable. Note that this isn’t the only option – it’s just for reference; there is a difference between theory and practice
In the first section of the medium-temperature furnace, the temperature rises from 300 degrees to around 470 degrees; the O2 content is 0.3%, and the surface temperature of the bed layer is 330 degrees. The temperature at the second point is 410–420 degrees, with an average of around 400 degrees – making this area the second place in the entire system with the largest temperature difference compared to the surrounding environment. It is recommended that the heat loss be around 3% of the reaction heat.
The heat loss of any device can be calculated based on the temperature outside its insulation layer. Conversely, the insulation layer of a device is also designed taking into account the desired level of heat loss. In actual operation, smaller devices have a higher proportion of heat loss, while larger devices have a lower proportion. Therefore, the actual heat loss of a device depends on its size and the conditions of its insulation layer, such as the surface temperature, degree of damage, and thermal conductivity of the lining material. Taking all these factors into account, 20 kcal/kmol can be used as an estimate for heat loss.
Heat loss = Surface area of the container * (Surface temperature of the container – Ambient temperature) * Total heat transfer coefficient. This equation can be used for estimation; one just needs to look up the value of the heat transfer coefficient.