Problem of synthetic heat sinks
Thread Content
During the major maintenance in February this year, modifications were carried out to reduce the pressure in the synthesis section; specifically, the original DN1000 short-tower was replaced with a standard DN1000 tower, and the capacity of the circulation pump was increased from 4 m3/h to 5.5 m3/h. The production capacity remained unchanged, with a daily output of liquid ammonia of around 142 tons. It has now been found that the temperature of the synthesis cooling coil is 4 degrees higher than that of the medium- and high-alcohol cooling coils (using the same circulating water, the temperatures were roughly the same before the technical upgrades); moreover, the outlet gas temperature varies for each group of the synthesis cooling coil, suggesting a possibility of flow deviation. The diameter of the main pipe of the heat exchanger is Φ127×21, while the diameter of the branch pipes is Φ49×10 (a total of 28 pipes). I have two questions for everyone: 1. Is the diameter of the main pipe too small? If so, should the calculation be based on the flow velocity (what is an appropriate value for the flow velocity? Some sources suggest 0.5–3 m/s for gases at pressures of 3–30 MPa), or should it simply be based on the sum of the cross-sectional areas of the branch pipes? 2. Is the area of the heat exchanger too small? What is an appropriate area? Thank you!
Calculate whether the circulation volume has increased; if the capacity of the original cooling exhaust pipes is limited, an increase in the circulation volume will lead to a rise in the outlet temperature.
The circulation volume has increased significantly; the simplest way is to check the design documents from that time, look at the design parameters and margins for the cooling fins, and the difference will become clear once those are compared.
This wasn’t included in the previous design documents, so the area is definitely insufficient; we’ll first enlarge the main pipe (we’ve already contacted the manufacturer) to address the issue of flow deviation.