The larger the difference between the hot and cold sections of a Stirling the more the efficiency rises. The heat sink is typically the environment the engine operates in, the ambient temperature. In the case of medium to high power engines, a radiator is required to transfer the heat from the engine to the
ambient air. Marine engines have the advantage of using the
cool ambient sea, lake or river water which is typically cooler than ambient air. In the case of combined heat and power systems, the engine's cooling water is used directly or indirectly for heating purposes raising efficiency.
https://en.wikipedia.org/wiki/Stirling_engine#Comparison_with_internal_combustion_engines
(In weather, ambient temperature refers to the current air temperature -- the overall temperature of the outdoor air that surrounds us. ambient air temperature is the same thing as "ordinary" air temperature.)
Sea surface temperature (SST) is the water temperature close to the ocean's surface. The exact meaning of
surface varies according to the measurement method used, but it is between 1 millimetre (0.04 in) and 20 metres (70 ft)
below the sea surface.
Daily, global Sea Surface Temperature (SST) data set produced on December 20th, 2013 at 1-km (also known as ultra-high resolution) by the JPL ROMS (Regional Ocean Modeling System) group
Weekly average
sea surface temperature for the
World Ocean during the first week of February 2011, during a period of
La Niña.
This image shows temperature changes in the ocean per depth (a) at night and (b) during the day
https://en.wikipedia.org/wiki/Sea_surface_temperature
"For our warm water environment, the optimal solution would be fuel-cell AIP."
Source:
https://defence.pk/threads/pakistan-navys-submarine-plans-s-20-vs-type-214.459191/#ixzz4PDhbXcPA
The Sterling AIP fitted operational submarines in Asia (Australian Collins class = Kockums design, Japanese Soryu with Kockums Sterling , Singaporean Archer class = modified Swedish
Västergötland) must all operate in sea water with relatively high surface temperatures. However, as you can see, sea water temperature drops off quite quickly beyond 10m depth. So, I doubt that the 'warm water' issue plays a big role except perhaps when operating in very shallow water. It may also be less of an issue when operating in the Arabian Sea closer to e.g. Strait of Hormuz or more towards Africa's Eastern shore, than farther out South /South-East e.g. way down India's West coast.
China's choice for Sterling type engines, together with the three sub classes mentioned says something of their ability to ALSO operate in relatively warm waters effectively and/or intened operating areas.
HOW BIG of a difference between Steling and fuel-cell AIP in this respect???? And how does that weigh in relation to other advantages/disadvantages of one type or the other AIP???
Thus far, in its ship export, China has often installed Western sensors and armaments, based on the customer requirements. I don't see why they shouldn't in the case of submarines. Indicative may be the submarine sale to Thailand. Also, many a Chinese system or sensor has a Western-European (Thales sonar e.g.) or US ancestor. This should ensure some degree of compatibility with sensors/equipment by Western-European or US producers, of not comparability. QUestion then becomes how different/similar are the products of Chinese versus non-Chinese producers.
As for VLS, there is to date no sub with VLS (for cruisemissiles, as opposed to ballistic missiles) operational in Chinese service
I am not aware Western manyfacturers are offering cruisemissile VLSs for submarines on the market. So, to the best of my knowledge, only the Russians have offered it (e.g. modified AMUR 950) and here too that particular VLS is not in operational service anywhere. Far more likely (and simpler) would be tube-launch. Though this may lead to a request for a larger displacement boat, which can store more rounds in total (e.g. 18 as in Kilo). Eight boats, each with e.g. 4 or 6 nuclear tipped cruise missiles could yield 2 boats at sea permamently, with 8-12 missiles which can be ripple fired in quick succession from existing torpedo tubes.