## 4 Discussion
The reason for the SCR showing the greatest rise is due to the increased average of the hot gas, thus indicating that the variation in temperature is more pronounced for the SCR. The opposite of this statement holds true for the IC, as it has the least variation across the temperature range because of the comparable hot gas outlet temperatures across the cycle inlet temperature range. Nonetheless, the degree rises of the counter-current design are only critical when the baseline heat sink outlet temperatures at 25 \({}^{\circ}\)C are considered. The IC has the highest baseline heat sink outlet temperature of 62.8 \({}^{\circ}\)C at a \(T_{1}\) of 25 \({}^{\circ}\)C for the counter-current design; the SCR has 22.5 \({}^{\circ}\)C  
Figure 12: Effect of Cycle Inlet Temperature (\(T_{1}\)) on Cycle Efficiencies. The trend shows decreasing efficiencies for all the cycles as the cycle inlet temperature increases. and the ICR is below the International Standard Atmosphere (ISA) temperature. This is evident in the significant differences of the temperature ratios between 25 and 35 \({}^{\circ}\)C in Figure 10 and is a stark contrast to the co-current design in Figure 11.  
The concern here is that the co-current precooler design is ideal for all cycle inlet temperatures as the heat sink exit temperature is not significantly affected. However, for a moderate heat exchange rate per square meter, the benefit of a compact design is compromised because a larger heat exchanger is required. On the other hand, the compactness offered by the counter-current design due to the high exchange rate per square meter results in excess outlet temperature of the heat sink. At these temperatures, a phase change (vapourisation) of the seawater would be observed, prompting the need for a condensation and return medium. This phase change will also increase corrosiveness in the heat sink passages. Although seawater has a maximum temperature of typically \(<\)40 \({}^{\circ}\)C in the hottest regions of the world, the expelled seawater could potentially increase the mean temperature of the incoming seawater, if the expelled water at the outlet is not recirculated effectively. Due to environmental constraints, the inlet temperatures into the compressor may be difficult to control. The problem becomes exacerbated in hot climates, which will result in reduced cycle output and investment return when compared to a much cooler climate for the same level of capital investment and initial operating costs. Figure 12 shows the effects of the analysed temperature range on the cycle efficiencies of all three cycles. With reference to Figure 12, the compressor inlet temperature affects the work demand of the compressors. This demand is quantified by the fact that for every 1 \({}^{\circ}\)C rise in the cycle inlet temperature, the effect is between a 0.3% to 0.5% increase in compressor work (\(W\)) of the cycles, which affects the useful work (\(W\)) available for the generator. The increase in CW correlates to the drop in cycle efficiencies of between 0.5% and 0.6% (direct delta percentage) per 5 \({}^{\circ}\)C increase. With consideration of this effect, it is important that the precooler design and recirculation of the heat sink is carefully implemented to avoid unfavourable cycle inlet temperatures, but more importantly for sound economics and to maximise the output against the operational costs. Furthermore, the choice of cycle based on the region in the world is very important. The IC has the lowest cycle efficiency but studies as part of this research work have demonstrated that the IC cycle efficiency can be significantly increased to make the cycle more competitive with SCR and ICR by increasing the COT of the reactor to temperatures in excess of 1000 \({}^{\circ}\)C [3].