Carl von Linde--scientist, inventor, global player.

INTRODUCTION

One of nine children in a Lutheran minister's family, Carl von Linde (Figure 1) was born in a village in upper Franconia/Bavaria (Figure 2). He grew up well educated in a typical middle-class family and spoke German and French by age ten.

While in high school in Kempten, Linde met the owner of a cotton spinning mill and was impressed by the mill's nozzles and steam engines, sparking his interest in engineering. Though his father wanted him to study theology, young Linde decided to study mechanical engineering at the prestigious Zurich Polytechnic. Among his teachers were Rudolf Clausius and Gustav Anton Zeuner, both of whom made significant contributions to engineering science by introducing entropy as an important indicator for calculations of machines and plants. Unfortunately, Linde's participation in a student protest against the school's director caused him to be expelled without a diploma in 1864; however, letters of recommendation from Zeuner and Reuleaux opened doors for further opportunities in the industry.

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Professional Work

In 1864, Linde's professional work began at the machine-building facilities of August Borsig in Berlin, where he constructed steam locomotives. Linde's duties included not only technical work but also the conducting and delivery of locomotives. In 1866, he married Helene Grimm (Figure 3), whom he had known since childhood, and went to Munich as director of the construction office of the newly founded Krauss Locomotive Company. The company's first locomotive, delivered by Linde himself, won a gold medal at the 1867 World Exhibition in Paris and can be found today in the Deutsche Museum in Munich.

SCIENTIST AND RESEARCHER

In 1868, the Technical University of Munich was established and appointed Linde as associate professor of mechanical engineering, but his meager salary could not support his growing family. Linde was forced to find extra income by writing and editing an industrial and commercial journal, Bayerisches Industrie- und Gewerbeblatt. Linde foresaw the importance of mechanical thermodynamics and soon made this the focus of his articles. As a result of his tremendous workload, Linde's health declined. In 1872, Linde took a hiatus from the university and took his family to Berchtes-gaden on the Obersalzberg in the Bavarian mountains, where he later built a house (Figure 4).

Linde's financial situation improved with an offer to go to Darmstadt University, and the Bavarian King installed him as a full professor on Christmas Eve in 1872. Linde then had the time and money to concentrate on teaching and writing and went on to found Laboratorium fur Theoretische Maschinenlehre, one of the first mechanical labs in Germany, for the practical training of students and for research.

At this time, Linde also was involved in many technical scientific societies and became an expert on steam boilers and turbines. His special interest in refrigeration technology began with a contest for the layout of a cooling system to crystallize paraffin. He analyzed the three refrigeration processes used at that time:

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* Evaporative cooling by means of vapor compression

* Evaporative cooling by means of vapor absorption

* Expansion cooling via exergy

The absorption machine was the most developed, but Linde discovered that all three systems were inefficient, as the efficiency factor reached only a fifth of the calculated maximum. Linde tried to improve the systems by calculating the caloric efficiency under different operating conditions using an ideal process he defined called "The Carnot Process." In this process, maximum efficiency has the value of one. Linde was not the first to use a cyclic process in refrigeration, but his background in thermodynamics enabled him to evaluate the development capacity for the refrigeration process. Linde published a paper, "The Extraction of Heat at Low Temperature by Mechanical Means" (1871), using a rigorous thermodynamic approach to refrigeration, and a second publication on that topic as well, "Advanced Ice and Refrigerating Machines" (1871).

Soon, his research focused on refrigeration using evaporation and the highly flammable refrigerant methyl-ether. Linde's fundamental knowledge of thermodynamics had found a chance for the future. As a result, he suggested the following improvements to refrigeration machines:

* To favor the vapor-compression machine.

* Operating the machine within the smallest temperature range possible to achieve the highest efficiency ratio.

* The use of mercury for stuffing boxes.

* Moving a pump seal between the piston rod and cylinder casing at the junction of the high inner and surrounding atmospheric pressure (to prevent the coolant from escaping).

In 1875, Linde presented his results at an International Congress for Brewery at the World Exhibition in Vienna. On that occasion, he met some important European brewers and used the opportunity to introduce his new technology. Until this time, the industry had used indirect cooling with natural or artificial ice, but brewers soon realized the benefits of direct cooling with refrigeration machines.

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Together with his student F. Schipper, Linde designed his first refrigerating compressor using methyl-ether. The first prototype was built in 1875 at the Maschinenfabrik Augsburg, later known as MAN. Linde's first system had major problems. More precisely, his first design seemed nearly impossible to make airtight, and a brewery machinist was seriously injured by refrigerant vapors. Afterward, Linde forbad machinists to test the machines. Linde's new construction of the stuffing box in 1875 dramatically improved the vapor-compression process, and he patented this revolutionary design (Figure 5).

The first prototype was assembled at a brewery in Triest, Austria, which is now in Italy. Despite some initial problems, this so-called "firstling" of Linde's ran flawlessly from 1877 to 1908 and can be seen today in the Technical Museum of Vienna. Early contacts with the influential brewers at the time (e.g., Gabriel Sedelmayer, Munich; Dreher and Faber, Vienna; Jacobsen, Copenhagen; Feltmann, Rotterdam and Hatt, Strasbourg) led to additional orders.

At the same time, Linde began research on ammonia compressors and subsequently built his first one, a vertical cylinder, in 1876 and his second, a double-action horizontal cylinder (Figure 6), in 1877.

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MANUFACTURING PLANTS

On June 21, 1879, Linde founded Gesellschaft fur Linde's Eismaschinen (Company for Linde's Ice Machines) in Wiesbaden, Germany, with less than 200,000 German marks, regarded even then as a substandard sum. His company, now one of the oldest manufacturing plants in Germany, was among the first to be a public limited company.

Linde's partners included Karl Lang, an advisory board member of many breweries; Heinrich Buz, Maschinenfabrik Augsburg; Gabriel and Johann Sedelmayr from Sedelmayr Breweries in Munich; Georg Krauss, owner of Krauss Locomotive Company; and Gustav Jung, Aktien Breweries Mainz. Linde gave up his university career to become CEO of the new foundation as an "employee entrepreneur," a strange arrangement in those days. He stayed with Linde's Eismaschinen as CEO until being elected to the supervisory board in 1890.

It was a difficult time for such a venture in Germany. The German Empire, established in 1871, plummeted into economic depression, but Linde remained optimistic. The demand for his refrigeration machines increased, especially his double-action horizontal compressor, which could easily be used in the low-ceiling fermentation cellars in breweries. As a global player, Linde saw opportunity in the international markets. Linde signed contracts with MAN in Germany, Sulzer in Switzerland, Carel Freres in Belgium, Morton in England, and the British Empire for the production of his ammonia compression machines, which soon became the leading products on the market. Linde was a visionary in business matters, uncommon in Germany around 1900, and most of his first employees worked outside Germany, planning and assembling new plants. One license for contracting Linde's machines was given to Fred W. Wolf, an early ASHRAE member, and company in Chicago.

Linde was the first to classify the different types of his refrigeration machines using roman numerals, and his competitors soon followed, making the Linde Classification of cooling machines the standard for the entire market for decades (Figure 7).

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Linde's Eismaschinen Company was very successful in selling machines to Argentinean sheep slaughterhouses for the cold storage of meat and in delivering mobile cooling machines to England for ships transporting cold meat over the Atlantic. Linde also advanced his inventions and products by developing new applications for them, such as ice skating rinks, which were very popular at that time. Linde's extensive knowledge of mechanics and thermodynamics was a scientific treasure for further development, and his work helped the society for his cooling machines, Society Linde, earn nearly legendary fame in the cooling business.

Ice Production Plants

Until the end of the 19th century, natural ice was the primary resource for cooling food. Sometimes though, warm winters caused insufficient ice harvests. In addition, bacteria and germs led to hygiene problems in the fermentation cellars of breweries. Always a businessman, Linde used these problems to promote the comparatively cost-intensive technical production of ice. Artificial cooling for the production and storage of food, especially all-important beer, morphed from luxury to necessity. By 1895, natural ice was still used during transportation but no longer used in beer production.

The brewing industry and the public slaughterhouses founded by the larger German communities soon made Germany the leading country in the refrigerating industry. As a second business, Linde started developing production plants for block and plate ice. As with the ammonia compression machine, Linde encountered obstacles as he explored this new application of cooling technology. The artificially produced ice was not translucent but had a milky appearance resulting from small air bubbles that developed during the cooling process. The "milky texture" of artificial ice was a massive problem; people thought high-quality ice should appear clear.

From the beginning, Linde insisted on superior quality, so he worked for a long time to develop processes that resulted in crystal clear ice. The first plant for artificial ice was built in Elberfeld-Barmen (later unified as Wuppertal). Further plants were erected in Stuttgart and Munich in 1880 and in Strasbourg in 1881. Although the production of artificial ice was expensive, the new technology was attractive to customers because of the continuous availability throughout all seasons.

Production of Refrigeration Machines

After several years of intense cooperation with different machine production plants throughout Europe, Linde concentrated on cooperation with MAN in Augsburg and Sulzer in Winterthur, Switzerland, to guarantee the high quality Linde was famous for. Linde also expanded his activities from planning and delivering refrigeration machines to offering complete refrigeration plants. Linde was deeply involved with procuring new customers, developing new applications, and obtaining licensing and patent contracts along with the rising problems of patent infringements.

In 1890 at age 48, Linde retired as CEO of his Eismaschinen Company and became chairman of its supervisory board. Linde kept this position until his retirement at the age of 89.

The Management

Communicating with customers and suppliers of Society Linde as well as procuring new customers made extensive correspondence and traveling a must for Linde. Naturally, the correspondence and travel options available at the time were not comparable to those available today, so Linde wrote by hand and his trips were long. Thanks to his copy books, 3,010 handwritten letters from 1876 to 1929 are archived. Linde's yearly tours around Europe also are documented.

BACK TO THE ROOTS OF SCIENCE

In 1892, Linde returned to Munich as assistant professor at the university and gave lectures on the theory of refrigerating machines. Just a few years earlier, in 1889, Linde founded an institute in Munich to test and compare refrigeration machines and demonstrate their accuracy and efficiency. This test institute was at one time associated with the Polytechnic Society of Bavaria. When Linde came back to Munich, he wanted to direct the institute in testing and developing refrigeration appliances. The board of Gesellschaft fur Linde's Eismaschinen was not smitten with the idea and thought "the institute too expensive and absolutely not necessary." Ultimately though, Linde did manage to convince the board.

Gas Liquefaction 

Research on the liquefaction of gases was at a point where small quantities of oxygen, nitrogen, and carbon monoxide could be produced. In 1894, Linde began research using very low temperatures and realized the commercial potential of gas liquefaction. Joule and Thomson had researched this topic already in 1857, and the so-called Joule-Thomson effect was part of the physics lectures at universities. Typically in that period, the available theoretical knowledge was not applied practically, and decades often passed before it was transferred into practical application. For example, the Joule-Thomson effect was well known, but, because the effect seemed only marginal, it was not applied.

At ambient temperature, the air temperature only diminished at 0.25[degrees]C (32.45[degrees]F) per one atmosphere of pressure drop. However, at lower temperatures, the effect increased. Linde's first approach was to cool the air down step by step by means of expansion. The cooled gas was led in counter-flow to the gas to be expanded, thus getting closer and closer to the point of condensation. Comparable ideas had already been published in 1857 by William Siemens and in 1885 by Ernest Solvay (inventor of ammonia-sodium-carbonate production) in a British patent specification: "I produce low temperatures by making a series of successive expansions of gas by mechanical power." Solvay tried to implement his ideas, but because of temperature losses and frictional heat, he could not get below -92[degrees]C (-133.6[degrees]F).

Linde's pilot plant was very simple. As a counterflow heat exchanger, he used a 100 m (328.08 ft) spiral pipe condenser, and the plant was assembled by his two assistant engineers, Negele and Moench, and his son, Friedrich. Surprisingly, the first test functioned perfectly. After several hours of cooling in the counterflow exchanger, the plant produced "liters of liquid air," as Linde reported later. He immediately delivered a telegram (Figure 8) to the headquarters of his society in Wiesbaden. [The text translation: "To Mr. Schipper Gesellschaft Linde Wiesbaden, May 29th, 1895 from Munich phone no. 25 7 50- Liquefaction of Air with best results achieved. We will keep the machine running until the end of the week and await your visit." Schipper, Linde's successor, was the CEO at that time at Wiesbaden.]

GLOBAL PLAYER

New Branch B in Hoellriegelskreuth Near Munich

The first office for Branch B, which dealt with gas and air liquefaction using the Linde patents (Figure 9), was in the Munich test center. As the production of oxygen became increasingly more important, a new plant was planned. In 1901, Carl Linde acquired a large site south of Munich in Hoellriegelskreuth with a direct railroad connection to the city. In 1902, an oxygen production plant was erected in addition to a manufacturing plant for liquefaction and separation applications. Most of the employees at that time were physicists and technicians. Some important inventions of Linde Branch B during the first years of the new century included:

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1900 Linde -- Air liquefier with ammonia precooling

1902 Linde -- Single-stage rectification column

1907 Linde -- Double-column air separation

Besides Carl Linde, the leading personnel of the new branch consisted of his sons, Friedrich and Richard Linde, and his son-in-law, Rudolf Wucherer. They each were there not because of their relationship to Carl but because they were excellent engineers or physicists.

From 1903 to 1920, Carl Linde became increasingly more active in the business. He established numerous subsidiaries in Europe and abroad, thus expanding the company's market and securing its gas engineering cartel with licensees all over the world. In America, it was Cecil Lightfoot, son of the English Linde representative. At that time, Linde already had close contact with Adolphus Busch from the famous Anhaeuser & Busch Breweries in Cleveland. In the winter of 1906-1907, Linde traveled to the United States. Accompanied by Cecil Lightfoot, he went to Buffalo, New York, to acquire a site for a manufacturing plant for oxygen. There, a man named Charles Brush was very helpful, and he would become Linde's business partner after Linde had problems achieving US patents for his inventions. The cooperation was more intense than Linde was used to, but together they were ultimately successful.

Linde and Brush invited 15 important "industry captains" for a business breakfast, and Linde made a presentation that resulted in all 15 entrepreneurs signing a treaty to found the American Linde Air Products Company. After 17 successful days in the United States, Linde returned to Europe on the steam ship Kaiser Wilhelm II. In 1913, eight years later, the Linde Company in America had 11 production plants. Unfortunately, the outbreak of World War I in 1914 stopped Linde's overseas activities, but he was able to continue his work successfully in Germany and other parts of Europe.

Membership in Technical and Scientific Societies

Early on, Linde became involved in various technical and scientific societies, some of which included the following.

Laboratories for Technical Physics at Munich University. These laboratories were established to give the students technical scientific training. Initially, this laboratory was located in his test center for refrigeration machines until a special building was built and was paid for by Linde, who raised funds from the German industry, VDI (Society of German Engineers), and from an industrial foundation.

Physikalisch Technische Reichsanstalt (German National Physical Technical Society). In 1895, Linde was nominated as a board member of the society. The society had only 20 members, but among them were the most famous scientists of that time. This group initiated many fundamental and practical research programs.

Akademie der Wissenschaften (Academy of Science). After many years of working in the industrial field, Linde was surprised when he was nominated for the Bavarian Academy of Science. His scientific work on gas and air liquefaction opened doors in engineering. In 1912, Linde presented the paper "Physic and Technique on the Way to the Absolute Zero Temperature." At the same time he was nominated as a corresponding member to the Imperial Academy of Science in Vienna.

Munich Polytecnic Society and VDI. During his time with Krauss Locomotive Company (1866), Linde was a member of the Polytechnic Society and joined it again when he returned to Munich in 1891. Linde also chartered the Bavarian Chapter of the VDI, the Society of German Engineers, and later was nominated as an honorary member of the chapter. The VDI in those years already had 10,000 members in 35 chapters. During his time as Member of the Board of the VDI, Linde met Count Zeppelin. Linde helped Zeppelin promote his ideas of building a rigid airship. Linde was elected president of the VDI in 1904 and 1905.

Bavarian Revision Society (Today TUV--Technical Supervisory Association). Linde, one of the founders, was nominated for president in 1892 and held the position for 25 years.

Deutsches Museum Munich. The Deutsches Museum in Munich (Bavaria) is known worldwide for its exquisite collection of machines and objects from the fields of technology and science. Linde was a board member from the inception of the museum, initiated by Oscar von Miller in 1903. The opening of the museum took place in the presence of the German Emperor and the Bavarian King. Moreover, German institutions and companies encouraged the support of the Deutsches Museum and continue to do so today.

DKV--German Society of Refrigerating and Air-Conditioning Engineers. At the first International Congress of Refrigeration in Paris in 1908, a national German refrigeration delegation was formed by VDI, and Linde was nominated leader of the group. The next year, Linde was elected as the first president of DKV. Forty-one nations were present at the congress, and Linde delivered a paper on air-conditioning of residential buildings.

As a result of this congress, the Association International du Froid (AIF, today IIR) was formed, and many national societies for refrigeration were founded. The next congresses took place in Vienna (1910) and Chicago (1913).

PRIVATE LIFE

Linde and his wife Helene had six children. (The family house at Wiesbaden is shown in Figure 10.) Their first daughter, Maria, married the psychiatrist Dr. Karl Ranke, and Linde helped him build his own hospital. Franziska married the Lutheran minister Seiler and lived in Dillingen. Anna married the Lutheran minister Michaelis in Bielefeld. Elisabeth married Rudolf Wucherer, later a board member of the Society for Linde's Eismaschinen. Linde's sons, Friedrich and Richard, married in 1898 and 1910.

Most of the daughters and sons and their families lived in close proximity to their parents and grandparents and kept close contact. Music played an important role in the Linde family, especially for Richard. He and his five children played string music on weekends. Together they easily formed a chamber music ensemble with violin, cello, and piano.

Carl Linde was fond of traveling and was often accompanied by his wife. They visited The Netherlands, the Isle of Wight, and various Italian cities, such as Rome, Florence, Naples, and Venice, and especially Sicily, to see famous pieces of art.

Linde also was an expert in walking and mountain climbing and, encouraged by his doctor, took long bicycle rides. Thanks to his healthy lifestyle, Carl Linde enjoyed a long life, dying at the age of 92 on November 16, 1934.

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Rudolf Plank, former DKV president and a member of the ASHRAE Hall of Fame, wrote in 1935:

    Linde represented a rare synthesis of profound scientific knowledge
    with technical understanding and a highly developed sense of
    reality, allowing him a wonderful harmony between theory and
    practice at an early stage of refrigeration engineering. He was
    ahead of his time, but managed to recognize the limits, and have
    ready solutions, when the particular issue was ready to be put in
    practice.

Linde's principles were carried on by his sons, Friedrich and Richard, by his son-in-law Rudolf Wucherer, and later by his grandsons, Johannes Wucherer and Hermann Linde. Since Hermann's retreat from the board of the Society in 1976, no member of the Linde family has taken part in the management of the Linde AG.

The DKV, the German Society of Refrigerating and Air-Conditioning Engineers, for which this author has had the honor and the pleasure to work during the last 35 years, honors Carl Linde's lifetime achievements in the field of refrigeration and cooling with an award for outstanding research, the Linde Gold Medal (Figure 11), which bears Carl Linde's profile.

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ACKNOWLEDGMENTS

Carl Linde's grandson Hermann Linde became the DKV president between 1967 and 1969. He is now 89 years old but is still very interested in the development of modern technology. The author is very grateful to him for the helpful information about his grandfather's life and to the Linde family for their help with preparing this paper.

The author would also like to express special thanks to Matthias Puhl and Hermann Linde for their support and encouragement.

The pictures in this paper are from the Linde Archives, Munich, and the DKV Archive.

BIBLIOGRAPHY

Dienel, H.L. 2004. Die Linde AG, Geschichte eines Technologie- Konzerns 1879-2004. Munchen: Verlag C.H. Beck oHG.

Dienel, H.L. 2004. Linde, History of a Technology corporation 1879-2004. New York: Palgrave MacMillan.

Dienel, H.L., E. Prandner, and M. Puhl. 2004. Der DKV und die Geschichte der deutschen Kalte- und Klimatechnik. Stuttgart: Alfons W. Gentner Verlag GmbH & Co. KG.

Linde, C. 1979 (reprinted original from 1916). Aus meinem Leben und von meiner Arbeit. Munchen: Oldenbourg Verlag.

Zeitschrift fur die Gesamte Kalte-Industrie 42. Jahrgang, 1935, pp. 161-213.

Irene Reichert

Associate Member ASHRAE

Irene Reichert is general manager of Deutscher Kalte- und Klimatechnischer Verein e.V., DKV, Stuttgart, Germany.