The efficiency of a forced draught boiler with dehumidified and cooled air depends on various factors, including the specific design and operating conditions. Let's break down the considerations:
Combustion Efficiency: Dehumidifying and cooling the air before it enters the boiler can potentially increase the combustion efficiency. When air is dehumidified, the water vapor content is reduced, resulting in a higher concentration of oxygen. This, in turn, can lead to more efficient and complete combustion of the fuel, thereby extracting more energy from the fuel and reducing waste.
Heat Transfer Efficiency: Cooling the air can enhance heat transfer efficiency within the boiler. Cooler air can absorb more heat from the combustion process, leading to higher boiler efficiency. It allows for a larger temperature difference between the combustion gases and the water/steam, improving the heat transfer rate.
Energy Cost of Air Conditioning: However, as you pointed out, the process of dehumidifying and cooling the air requires additional energy input, usually in the form of electricity. This energy consumption needs to be taken into account when evaluating the overall efficiency of the system.
To determine whether it's more efficient to dehumidify and cool the air, a thorough analysis is required, considering the specific boiler system, the fuel used, the cost of electricity, and the environmental conditions in which the boiler operates. Factors such as the fuel cost, energy efficiency of the air conditioning system, and the boiler's overall efficiency play a crucial role in this evaluation.
For modern ocean liners or industrial applications, where fuel efficiency and environmental considerations are vital, such measures might be worth exploring. However, for historical ocean liners from the early days of air conditioning, the primary focus was likely on passenger comfort rather than optimizing boiler efficiency. Air conditioning was a luxury amenity, and the energy costs associated with dehumidifying and cooling the air might not have been a primary concern at that time.
In summary, the idea of dehumidifying and cooling the air for a forced draught boiler has the potential to improve efficiency, but the additional energy required for air conditioning should be carefully evaluated to ensure that the overall system remains economically viable and environmentally beneficial.