Which absorbs more heat per unit of time: water at 100 degrees boiling or water at 50 degrees boiling (under negative pressure)?
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RT assumes the use of 120-degree steam for interwall heat exchange of the material. Under negative pressure conditions: In Case 1, the pressure is 20 kp and the boiling point of the material is 58 degrees; in Case 4, the pressure is 55 kp and the boiling point is 70 degrees. In the case with a higher pressure, more 120-degree steam is consumed per unit time, while this condition results in a better effect of evaporation and concentration of the material. Determine this and provide the reasoning
P T h″ /MPa /℃ /(kj/kg) 0.012 49.4458 2591.2 0.013 51.0617 2594 0.1 99.632 2675.4 0.11 102.317 2679.6
It is common sense that if it is only heated to the boiling point, water at 50 degrees will absorb less heat. If boiling is maintained, that is, continuous evaporation occurs, water at 100 degrees Celsius requires 2257 kJ/kg of energy for boiling and evaporation, while water at 50 degrees Celsius requires 2382 kJ/kg; thus, more heat is absorbed per unit of time.