THE 34^th Congress on Heating, Refrigerating and Air-Conditioning was held in “Sava” Center in Belgrade, 3^rd-5^th December 2003. Association for Heating, Refrigerating and Air-Conditioning (KGH) with Association of Mechanical and Electrical Engineers and Technicians of Serbia (SMEITS) organized the Congress. The Congress was organized with the accompanying exhibition, under the following motto: ENERGY, ECOLOGY, ECONOMY, EFFICIENCY AND KGH.

International lecturers, exhibitioners and authors from USA, England, Germany, Denmark, Sweden, Norway, Italy, Austria, Hungary, Bulgaria, Turkey, Swiss, and Romania as well as from Slovenia, Croatia, Bosnia and Herzegovina and Macedonia participated on this Congress. The official languages were Serbian and English. All the papers were translated simultaneously from English into Serbian and from Serbian into English.

The accompanying exhibition in Center “Sava” was an important display where over a hundred domestics and international exhibitioners efficiently presented everything that is essential for practice, designers and manufacturers of HVAC&R systems.

General patron of the 34th Congress was HVAC Cluster, Slovene Heating Ventilation and Air Conditioning), Godovič, Slovenia.

General sponsors of the 34th Congress were DBDH, Danish Board of District Heating, Denmark; IMI INTERNATIONAL, Belgrade; IMMERGAS SPA, Belgrade; MONTAŽA, Belgrade; and TERMONET, Belgrade. Except General patron and General sponsors there were 63 sponsors from our country and abroad to support this event.

Plaques “KGH”, medals and acknowledgements for outstanding results in the previous year were given out to experts and firms during an evening party in the restaurant of Center “Sava”, at the of the second  day of the Congress.

Technical Program of the Congress in the Congress hall of the Center “Sava” was plenary, closing throughout all three days with thematic groups of lectures: Introductory papers (7 papers); Renewable Energy Sources (7 papers), District Heating Systems, (12 papers); Buildings and Energy (8 papers); Apparatuses and Devices and in HVAC&R Systems (10 papers); Energy, Fuels and Tangential Problems of HVAC&R (5 papers); Application of the Refrigeration (7 papers). Periods between thematic sessions were used for presentations of the Congress Sponsors.

After the opening word of the President of the Congres Organizing Committee, Prof. Branislav Todorović, Ph.D., B.S., the Congress auditorium was welcomed and the Congress opened by Prof. Dragoslav Šumarac, Ph.D., Republic of Serbia Minister of Structure and Development, Prof. Dragan Domazet, Ph.D., Republic of Serbia along with the Minister of Science, Technology and Development, official representatives of American Society ASHRAE, Richard H. Rooley; Dean of Faculty of Mechanical Engineering, Belgrade, Prof. Miloš Nedeljković, Ph.D., B.S.; of Thermal Association, Prof. Milan Radovanović, Ph.D., B.S.; and Nenad Pavlović, B.S., from the Agency for Energy Efficiency.

President of the American Society of Heating, Refrigerating and Air-Conditioning Engineers – ASHRAE, SAD, Richard H. Rooley, having given the complimentary word continuited with the preliminary report, AIR CONDITIONING AND REFRI-GERATION VITAL TO BUILDINGS IN INTERNA-TIONAL COMMUNITIES in which he addressed the HVAC&R industry and the role of ASHRAE in the industry worldwide. Furthermore, it deals with the changes in the construction industry and indicates the actions that must be taken by HVAC&R engineers and ASHRAE within the entire construction community.

In his paper ENERGY FOR XXI CENTURY Prof. Nenad Đajić, Ph.D., B.S., Faculty of Mining and Geology, Belgrade, discusses the influence of production and consumption of energy on the sustainable development considered globally. The energetic will be come more and more significant, because the energy demands are growing, both due to the increase in the population and the standard of living all over the world. From 1950 to 1970 the world consumed more energy than in the period of development till then, i.e. than the consumption level in the 1950 the consumption rate between 1960 and 1970 was about 4,6% higher.

In the paper VIZUELIZATION OF ENERGY BALANCES BY DURATION DIAGRAMS, Prof. Enno Abel, Ph.D., B.S., Building Services Engineering, Taastrup, Denmark, has presented an example how the understanding of the processes behind the indoor climate and energy needed for obtaining a certain climate can be facilitated by parallely visualisating and running simulations and calculations. A comprehensible way to do this is to illustrate the processes by duration diagrams.

In the paper SUSTAINABLE BUILDINGS BY MEANS OF ENE-RGETIC OPTIMIZED AIR HANDLING SYSTEMS, Prof. Michael Haibel, Ph.D., B.S., Department of architecture and building climatic, Biberach University of Applied Sciences, Biberach, Germany, describes the present and future development in architecture and building sciences and requirements for building service and handling in air systems. It is shown that the reduction of the air flow velocity by a slight enlargement of units and ducts and the optimized pacement of fans leads to a significant reduction of the annual operation costs. Furthermore, the heat recovery systems and variable air volume may lead to the energy and cost saving potential of up to 50%.

Prof. Nenad Kažić, Ph.D., B.S., from Faculty of Mechanical Engineering, Podgorica has observed interaction between development of society, energy consumption and environment protection in the view of the Second Law of Thermodynamics in paper ENERGY, ECOLOGY AND SOCIETY – A THERMODINAMICAL ASPECT. The consumer society today uses up huge quantities of the limited natural resources. The developed countries are now conscious that the substantial planetary problems can not be solved by the brutal reasoning of the consumer society, but a new view of the world has to be created. The new paradigm has to be based on sustainable development of the society, introducting “the minimum production of entropy”, as a fundamental principle of the new era. The process energy analysis is one of the ways of analyzing the process in harmony with the principle mentioned.

In the paper GLOBALIZATION IN STANDARDI-ZATION, SPECIFICALY IN THE HVAC FIELD, Aleksandar Raković, Ph.D., B.S., Polytechnic Academy, VTŠ, Belgrade, gives a critical review with some of the cases when the adopted standards or regulations were not complied with. Although the SI, units have been adopted in technically highly-developed countries like: USA, Great Britain, Canada and the others, continue to use the Anglo-American units (e.g. barrel, bushel, ounce, Btu/h etc.). Also he has expressed his own standpoint on banning the usage of halocarbon compounds – freons as refrigerants and destroyers of the ozone layer, using asbestos in building constructions and restrictions of the heat characteristics of the building.

Prof. Emin Kulić, Ph.D., B.S., and Haris Lulić, B.S., from the Faculty of Mechanical Engineering, Sarajevo, presented technological and functional scheme and brief description of the experimental-test station's operation in the paper METHODOLOGY FOR DETERMINING THE BASIC THERMAL CHARACTERISTICS OF FLAT WATER-COOLED SOLAR COLLECTORS ON THE AUTHOR’S OWN TEST STATION ACCORDING TO THE PROCEDURE OF EN 12975-2 STANDARD,. The recent measuring results obtained the procedure given in the title have been analyzed and compared with the data obtained according to 1978 ASHRAE procedure.

In the paper MEASURING OF ENERGY CONSU-MPTION IN DISTRICT HEATING SYSTEM IN NEW BELGRADE'S BLOCK 34 Branislav Živković, Ph.D., B.S., and Maja Todorović, M.Sc., B.S., from Faculty of Mechanical Engineering, Belgrade, presented the reduction in energy consumption for heating, applaing thermostat valve and heat distributor in the buildings in New Belgrade. Also, the results obtained by recent measurings show a decrease consumption for heating of over 10% annually and a reduction of about 40% of electric power consumption with the implementation of variable rotation pump.

The paper APSOLUTE FILTER TESTING ACCORDING TO “PAO SCANING” METHOD, Mateja Erjavec, B.S., IMP Klima, Godovič; France Saje, B.S., VTŠ, Novo Mesto; and Egon Venko, B.S., Institute KGH, d.o.o., Godovič, Slovenia; shows different units for absolute air filtering with HEPA filter as a necessary element in pharmaceutical, food-processing, chemical and electronic industries, microbiological, microfilm and nuclear technologies, as well as in hospitals, operation theatres and laboratories. The paper also provides instructions for HEPA filters testing. Furthermore, the standards for room classification and testing are given.

In the paper COMPARISON OF METHODS FOR THE DEFINITION OF ACOUSTIC POWER OF HVAC DEVI-CES BY MEASURING THE ACOUSTIC PRESSURE, ACOUSTIC INTESITY AND VIBRATION, by Nikola Holeček, M.Sc., B.S., and Marjan Semprimožnik, B.S., “Gorenje” d.d., Velenje, Slovenia, demonstrates the acoustic power determination by a practical example, according to the mentioned methods in anechonic and echoic room. The obtained results were discussed and impacts of disturbing inputs on the relative measured failure analyzed.

The paper, GENERATOR GAS BASED ON BIOMASS AND BIOBRIQUETTES, by authors prof. Dragan Mitić, Ph.D., B.S., Faculty of Work Safety, Niš, Bratislav Simonović, B.S., and prof. Aleksandar Stefanović, Ph.D., B.S., Faculty of Mechanical Engineering, Niš, and Emina Mihajlović, M.Sc., B.S., Faculty of Work Safety, Niš, and the paper, ADVANTAGES OF USING SPECIALLY DESIGNED BRIQUETTES FOR FIREPLACES, by authors Emina Mihajlović, M.Sc., B.S., Faculty of Work Safety, Niš, prof. Dragana Mitića Ph.D., B.S., and Slobodanka Janković, M.Sc., B.S., Faculty of Work Safety, Niš, presented their own experimental results in applying biomass for the process of gas generation and assessment for its possible application, as well as using fireplace briquettes exclusively made of biomass waste and specially designed for fireplaces, with properties that make them suitable for application.

Prof. Marija Todorović, Ph.D., B.S., and Olivera Ećim, M.Sc., B.S., Department for Energy Efficiency and Renowable Energy Sources of University in Belgrade, VEA, Belgrade, have presented two papers: HYBRID SYSTEMS OF SOLAR ENERGY USE FOR AIR CONDITIONING SYSTEM OPERATION AND SANITARY WATWE HEATING which demonstrates the investigation of working dynamics and the possible energy effect when active cooling photoelectric systems with a concentration of solar irradiation from  illuminated homes is applied; and POLYVALENT ENERGY FACADES AND INTEGRATED SYSTEMS THAT USE RENEWABLE ENERGY SOURCES IN BUILDINGS, which presented the development of physical model for optimization function of polyvalent energy facades (heat load, daylight, heat and photovoltage conversion and the use of solar energy) and the development of optimal control model of a system for economical and efficient use of solar and geothermal energy, waste biomass and solid urban waste.

Agency for Energy Efficiency Government of the Republic of Serbia presented the following papers: PROGRAM OF BUILDING ENERGY EFFICIENCY, Predrag Pažin, and PROGRAM OF ENERGY EFFICIENCY IN COMMUNAL ENERGETICS, Saša Nedeljković, promoted the aim and activities of Agency for Energy Efficiency for rational use of energy in these fields. The Agency was founded by the Republic of Serbia Government with technical and financial assistance of the European Agency for Reconstruction.

In the paper DESIGNING OF AIR-CONDITIONERS FOR THE PASSENGER CAR, Rade Alimpić, B.S., “21 oktobar”, Kragujevac, defined the technical requirements for designing the air-conditioners for passenger car. The method of calculation of these requirements is also presented. The air-conditioner test procedure in the tunnel is reviewed according to TU FIAT-C.510 (simulated urban traffic) and C.515 (simulated intercity traffic). The possibilities of air-conditioner components production in the company “21st October” in Kragujevac are also discussed.

Prof. Branislav Todorović, Ph.D., B.S., from Faculty of Mechanical Engineering, Belgrade, in the paper REFRIGERATION AND AIR-CONDITIONING – AMONG THE MOST IMPORTANAT DISCOVERIES OF XX CENTURY gives a chronological account, of the registered items and discoveries, in the field of refrigeration and air-conditioning throughout the human history.

At the and, Prof. Branislav Todorović, Ph.D., B.S., President of the Congress Organizing Committee, presented his own views and summarized the prior Congress practice. He concluded what was widely acclaimed by the auditorium, that this year's Congress demonstrated a high professional and scientific level of both thought and practice improving yearly towards more distinguished international achievement, behaving in mind the impressive number of exhibitioners (over a hundred), papers (56 according to Congress program) and more than 500 participants from our country and abroad.