The family moved to the Hague and after his schooling there at the Netherlands Lyceum, he enrolled at Leiden in 1925 to study physics. Even before his graduation in 1932 he started an investigation in the Kamerlingh Onnes Laboratory under Professor W.H. Keesom. In 1934 he presented his results in a doctorate thesis: 'Investigations of solidified gases by means of X-rays'.
In between these academic achievements he found time in 1933 to get married, to Zwaanhilde Casimir (daughter of his former headmaster), and also to start work, early in 1934, at the Philips Company, Eindhoven, in the research laboratory. As was usual in that establishment, K6hler was put to work on a topic quite remote from the subject of his thesis. For some two years he worked on a system of optical telephony. The equipment developed had a range of 4.5 km under good weather condition's, no little achievement at that time, long before the transistor and the laser. This was followed by further work in electronics, including signal distortion in amplifiers and the development of a precision form of Wien's bridge. Near the end of the war, after Eindhoven had been liberated in September 1944, K6hler served for a period with the British Army.
In 1946 he opted to work in a group set up earlier (1938) by H. Rinia to develop the hot air engine (Stifling engine). The original intention had been a prime mover for a small electric generator to power radio sets in remote areas of the world. However, the work done secretly during the war had made such progress that the engine seemed to have much wider promise for the future. It had also been shown that when the engine was not heated but instead driven, it acted as a very effective heat pump or refrigerator.
K6hler had a certain leaning towards mechanical engineering and felt drawn to the engine project, with its well-defined practical objective. He joined the group in January 1946. In March, however, Rinia asked him to start a separate group to look into the Stifling cycle for cooling purposes. He said later (1973): '... when I spoke to Rinia I heard, to my great disappointment, that I was not to work on the engine; no, I was to develop the refrigerator. And, frankly, it didn't