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On the thermal comfort of a man staying outdoor during the summer affect mostly meteorological factors, physical activity and the type of clothing. The work analyzed external air parameters, such as: temperature, relative humidity and wind speed, occuring in years 1997-2016. Meteorological data recorded at the Rzeszów-Jasionka station allowed to determine, among others, the occurrence of maximum daily and hourly temperatures of outdoor, the daytime and hourly air relative humidity, the hourly wind speed, as well as the relationship between these parameters. In recent years, it has been observed the increase of the number of hot and very hot days which indicates a warming of the climate. The duration of series of days with maximum daily temperature above 30°C is also prolonged, which is not comfortable for a person staying outside. During summer, during hot and very hot days, the average relative humidity remained below 70%. The daily course of this factor was characterized by the opposite tendency with respect to temperature. The wind speed in the summer season varies from 0 to 6 m/s. On a daily basis, the increase in wind speed occurred in the afternoon hours which is consistent with the temperature characteristics. The occurrence of wind during the hottest hours causes a pleasant cooling of the organism.

Security in heat supply systems plays an important role in social, technical and political terms. It includes three main components: energy security, security of heat supply, security of people. The differences concern the subject, area, scope, as well as the degree and purpose of the analyses. The article is a continuation of research conducted by the author, presenting the concept of security of heat supply as a necessary “umbrella” supported by reliability and system resilience to threats, constituting a set of actions aimed at minimizing the risk. The subject of the analysis of this article is the security of heat supply, analysed in the context of heat supply management to recipients and risk analysis related to the lack of heat supply. The elements of decision theory were used as adequate for this purpose. Different configurations of heat distribution in the system have been taken into account when determining the expected values of risk related to the occurrence of power limitation for various degrees of restrictions and various network configurations. The author’s use of elements of decision theory in heat supply systems illustrated at the work gives the opportunity to assess and manage the security of heat supply to the recipient. It takes into account the possibility of different heat distribution configurations in the system at the operational stage, as well as may be the basis for optimizing changes in the distribution of power supply areas and selecting the most advantageous network configuration at the design stage.

Abstract. District heating systems as strategic objects from the point of view of state security must ensure reliability and security in supply of heat to their customers [1,2]. Thanks to computer simulation methods, district heating companies can analyse the operation of the heating networks at the design and operation stage. Computer simulations also offer a wide range of possibilities in the aspect of optimization of the district heating operation as well as prediction and analysis of network failure effects [3][4][5][6]. The paper concerns the simulation of a district heating network. The methods for the simulation of heating networks were characterized and simulations of district heating system were carried out. The effects of the failure were analysed at different values of outside temperatures and for different durations of failure. The value of compensation for undelivered heat was also determined. Simulations were carried out for an actual district heating system located in Rzeszow.

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