Heat transfer efficiency of a heat exchanger with compressor outlet flow as the heat flux

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Our company’s reboiler is powered by propylene supplied by a compressor; when there are fluctuations in the compressor’s operation during the day, the outlet pressure decreases, which results in a reduced flow of propylene reaching the reboiler. Automatic valves then open to increase the flow rate, but even when these valves are fully open, the flow rate still isn’t sufficient. Nevertheless, the heating effect of the reboiler increases. When the pressure at the compressor outlet increases, the flow rate of propylene going into the reboiler rises. The automatic valve then closes gradually, but the heating effect of the reboiler decreases. Why is this? The explanation might be a bit verbose, so I’ll use numbers to illustrate the two scenarios. Scenario 1: The pressure at the compressor outlet is 1 kilogram; the flow rate of propylene supplied to the reboiler as a heat source is 100 standard cubic meters. In this case, the opening degree of the valve supplying propylene is 50%, and the temperature at the bottom of the tower is 10 degrees. Scenario 2: The pressure at the compressor outlet fluctuates to 10 kilograms; the flow rate of propylene supplied to the reboiler as a heat source remains 100 standard cubic meters. However, due to automatic control, the valve opening degree adjusts automatically to 10%, and the temperature at the bottom of the tower is 12 degrees