Technology to prevent snow accumulation on the roofs of buildings operated by a transport company as a solution to snow removal problems

. As part of a competition of projects aimed at solving strategic problems ensuring the sustainable development of the Krasnoyarsk Railway company, a technology for removing snow from the roofs of buildings was proposed, which is conceptually different from its analogues. The technology is based on the use of compressed air and automatically prevents the accumulation of snow, preventing its deposition on the “approach” of the roof; it does not provide for the use of moving, vibrating units, scraper parts, or thermal elements that negatively affect roofing coverings. Automatic, manual, remote control and notification modes are provided. The main results of verification of theoretical studies are presented: data from experimental studies obtained on a model of a snow removal installation under conditions simulating real operating conditions are presented. The possibilities of optimizing the technology for various types of roofs, social, environmental and economic feasibility for wide application are shown.


Introduction
Most of the climatic zones of Russia are characterized by large amounts of precipitation in the form of snow during the cold season.In March-April, the Russian northern spring is in full swing, and in the annual cycle of the Earth this is the snowiest period.By this time, 19% of the planet's surface was covered with snow, the area of the snow blanket reaches 95 million km2, and its mass is 13,500 billion tons [1,2].

The problem of roof collapses
The gigantic weight of the snow cover at this time can even influence the speed of the Earth's rotation.Heavy snowfalls can destroy the roof structure, cause its collapse and death, and paralyze the infrastructure of cities and even countries.At first glance, it is difficult to believe that soft snow can push through a roof, but if you consider that 1 m 3 of "stayed" snow can weigh more than 300 kg, it becomes clear that the danger is real [2].
The influence of natural disasters on technosphere objects systematically causes disasters and entails huge costs for their prevention and elimination of consequences.Here are just a few examples of disasters caused by snow accumulation on roofs.In February 2006, in Moscow, the roof of the Basmanny Market collapsed on an area of 2000 m2, a fire started under the rubble, which was extinguished only after 17 hours, 66 people died, 32 were injured.In February 2010, a number of cases occurred in Moscow: a wall and part of the roof of an exhibition pavilion collapsed in Sokolniki with an area of 6000 m 2 ; The roof of a hangar at an automobile plant in the south-west of Moscow with an area of 100 m 2 collapsed; fortunately, there were no casualties or injuries.In the same year, a glass roof collapsed in the O'Key hypermarket in St. Petersburg, and one person was found dead under the rubble.In January 2011 in St. Petersburg at the sports complex named after.Alekseev, 100 m 2 of roof collapsed, resulting in 2 injuries.In February 2011, three spans of the roof of a plant with an area of 170 m 2 collapsed in Novosibirsk.Two people were killed and five people were injured.A similar incident occurred in Kazan.The roof of the warehouse could not withstand the weight of the accumulated snow -480 m 2 collapsed overnight.As a result, 5 people died.In March 2011, in the Pyramid shopping center in the village of Balashikha near Moscow, part of the roof on an area of about 20 m 2 collapsed, one person was injured.In Chelyabinsk, part of a warehouse collapsed, no one was injured.In February 2020, in Novosibirsk, the roof of an extension to a café building with an area of 240 m 2 collapsed, 2 people were killed, 4 were injured, 190 were independently evacuated before rescuers arrived.In February 2022, the roof of a school with an area of 700 m 2 collapsed in the village of Ashukino near Moscow; victims were miraculously avoided [3,4].This sad list, unfortunately, can be continued.

Problem of snow and icicles falling from roofs
Every year, roofs collapse, icicles fall, snow melts off the roofs in many cities, including Krasnoyarsk, the damage caused to people and buildings is recorded, and criminal cases are initiated.During a thaw, additional problems arise: an even greater increase in pressure on the roof, the formation and fall of icicles, and leaks of the roof covering.According to statistics, in large cities of Russia, every winter more than 50 people and more than 300 cars are damaged from icicles and pieces of ice falling from roofs alone [5].

The problem of injuries during roof cleaning
The work on cleaning roofs manually (mechanically) which seems quite simple is in fact always associated with the risk of work-related injury, including death.In the housing and communal services system, random people who do not have the proper qualifications are often involved in cleaning roofs.For cleaning, mechanical methods are often used with the involvement of temporary workers (or the distraction of organization employees from permanent work).All mandatory conditions established by labor protection legislation: safety training when working at height once every 3 years, knowledge testing, work experience at height, provision of special personal protective equipment, technical equipment -employers often ignore.Violation of labor protection requirements is punishable by the Code of Administrative Offenses and the Criminal Code of the Russian Federation.This entails the payment of compensation to victims, administrative and criminal liability, increasing the tension of the employer's labor process.
According to official data from the Russian Ministry of Labor, of all requests by Russians to medical services in 2022, more than 37 million were due to falls from heights, of which 646 thousand people died.1933 accidents were recorded, of which 303 were fatal.Falls are the cause of more than 33% of industrial accidents and losses of 600 thousand man-days in the Russian economy [4,5].Official data presented in the State Report "On the activities of the State Labor Inspectorate in 2022" confirm the information from global and domestic statistics on the causes of injury that most often (26.8% of cases) injuries to people in the Krasnoyarsk Territory occur due to a fall from a height.An analysis of the consequences of a fall from a height showed that for every 690 cases, 1 is fatal, 4 involve permanent disability, 13 require hospitalization for 10 days, 24 cases involve hospitalization for 1-9 days [5].
The Krasnoyarsk Railway, with a length of 3157.9 km with 590 stations, operates more than 1000 buildings that need to clear their roofs of snow in winter.The problem of timely removal of snow and icicles from roofs in general for large Russian cities, and for Krasnoyarsk railway buildings in particular, remains difficult to solve and relevant [6].

Assessment of technological uniqueness of the technology
Currently, there are a large number of different methods for clearing snow from roofs: mechanical cleaning, technical methods (automatic scrapers with a copter and video camera used for remote monitoring and control, electrical emulsion devices, heating systems), the use of anti-icing coatings (the use of superhydrophobic nanocoatings), a preventive method ( selection of the optimal roof slope, heat and vapor insulation, attic ventilation), chemical method (application of liquid and solid reagents) [7][8][9][10][11][12].In Russia, there are patented automatic and human-controlled technologies and devices for cleaning roofs using compressed air [13,14].The companies known abroad are "DIY Snow Removal", "Snow Rescue", "Snow Remover", "Automatic Snow Clearing Device", which use compressed air to remove snow with a scraper mechanism.Most of the automated devices are aimed at removing snow that has already accumulated on the roof, are equipped with bulky parts: scrapers, rails, cables, moving, rotating devices, are heavy, and require human presence.This will reduce the possibility of using the equipment in conditions of low temperatures and strong winds, indicating the unreliability of such devices, which do not have versatility and aesthetics.Evidence of the effectiveness of their use has not been publicly published.
The technology developed for automatic warning of snow accumulation eliminates all these disadvantages.

Problem solving
Analysis of the problems of snow accumulation and snow removal allowed us to come to the following conclusions: 1. Statistics of accidents associated with snow accumulation on roofs and falls when working at height indicate the unresolved problem of timely safe clearing of snow from roofs.Most cases of snow falling from the roof without causing injury to people go unnoticed; there are no real statistics on such events; this may explain the impossibility of an objective assessment of risks and people's awareness of the reality of the threats.2. The main cause of disasters is untimely cleaning of roofs from ice and snow.Experts from the Russian Ministry of Emergency Situations register two reasons for roof collapses due to snow accumulation: first, the actual snow load exceeded the design load limit due to unforeseen weather conditions (up to 140 kg/m2); the second -the actual reliability of load-bearing structures -is lower than the design one (SNiP 23-01-09).3. Problems of snow accumulation on roofs can be solved simultaneously in several directions:  At the building design stage -designing optimal pitched roofs without valleys and "pockets" and "bags" with an angular slope parameter of the roof slope of more than 40-60°, on which snow does not accumulate and icicles do not form. Modernization of existing roofs -taking into account parametric, aesthetic and urban goals.Economically, modernization is advisable when several problems are solved at once.For example, in the central part of large cities with dense buildings with historically valuable architecture: increasing the functional area on the roof (sometimes 3-4 floors), making a profit through the exploitation of these areas; the use of modern reliable structures, forms that harmoniously fit into the architecture of the urban landscape and, at the same time, fundamentally exclude snow accumulation. Carrying out a set of special measures for public utilities: careful analysis of weather forecasts, systematic monitoring of critical sections of roofs using automated systems and their timely cleaning.Today, the risks are due to the fact that in most cases the moment of making a decision on snow removal is characterized by uncertainty and is based on a person's subjective visual assessment of the volume of snow accumulation. One of the promising areas that eliminates injuries and deaths as a result of snow accumulation may be the developed technology for automatically preventing the accumulation of snow on the roof.

Design aim and objectives
Patent research, analysis of domestic and foreign experience in the field of snow removal of roofs using engineering methods have revealed the conceptual uniqueness of the technology being developed, aimed not at clearing already accumulated snow, but at automatically preventing its accumulation, without the use of moving, vibrating, heated elements.When designing a technology (method) for preventing the accumulation of precipitation on the roof, we were guided by specific technological requirements and climatic conditions specified in the technical specifications of the customer -the Krasnoyarsk Railway company -for the actual roof of a station building located at one of the railway stations.
The project goal is to develop a technology and device that should ensure the removal of snow from the roof by preventing the formation of sediment deposits (snow), eliminating the formation of "snow bags" in valleys, places of difference in roof heights over an area of up to 90% of the roof and a snow cover thickness of more than 3 cm.
Project tasks are as follows:  to ensure the possibility of installing the device and using the technology on the operating roofs of the company's buildings, ensuring the integrity of the roof truss structure and using protective aprons when removing structural elements through the roof covering;  to ensure effective prevention of the accumulation of snow precipitation on the roofs of various types of buildings, excluding its accumulation in difficult areas;  to provide the ability to automatically control the prevention of snow accumulation on the roof of buildings, reducing labor costs and injuries;  to ensure the minimum possible metal consumption without reducing the functional efficiency of the structure, fire and explosion safety;  to ensure a reduction in capital investments, energy resources and material costs, and the aesthetics of the design.
At the theoretical level, the following methods were used: abstraction, idealization, formalization, analysis-synthesis, induction-deduction, axiomatics, generalization.In order to assess the fundamental possibility of obtaining a workable installation, we carried out patent and theoretical studies using the physical laws of hydro-gas dynamics, performed aerodynamic calculations, decided on the type and performance of blowing equipment, created a preliminary design of an aerodynamic route and a model of an experimental roof.At this level, a logical study of the collected facts was carried out, concepts, judgments, and conclusions were developed.They correlated early scientific ideas with emerging new results, made theoretical generalizations, and formed a feasibility study.At the metatheoretical level system analysis, modeling, design were used.We developed ways to build the foundations of snow removal technology using the theory of jet flow, established the boundaries of its application, and made a theoretical calculation of the parameters of free axisymmetric air jets.We created 3D models of the experimental installation, prototype, nozzle distributors using the Blender 3D editor and the SolidWorks Flow Simulation computer-aided solid-state design system.We made a preliminary selection and determined the nozzle parameters for the given dimensions and angular parameters of a hip-type pitched roof.We have developed recommendations for the use of technology for various types of roofs.
At the empirical level, we used the following methods: observation, comparison, counting, measurement; we accumulated experimental data, generating statistical facts and their description.These methods were used in the formation of design and technological documentation, construction of a roof model, installation of an aerodynamic system and integration of an automatic device control system.
The research program with the content of the stages is given in Table 1.

Results
During the research, projecting and testing of the prototype, results were obtained for each stage.Technological parameters and recommendations for using the technology for various roofs were developed.

Results of theoretical and laboratory studies
Significant factors of the range of free axisymmetric air jets have been determined: blower power; minimum resistance to air flow, mode of air movement (turbulent), speed and type of jet: minimum significant speed 1.5-2.0m/s, free jets (do not have solid boundaries); type of free jet: incomplete (laying on the surface) -the Coanda effect (flotation effect) increases the range of the jet compared to a full jet by 1.4 times, achieved by adjusting the nozzle angle relative to the roof angle; shape of the nozzle outlet: the jet emerging from the slotted hole of the nozzle is advantageously distributed (expanded) in width over an ordinate distance of 2 m, minimizing the area of "blind" zones between the nozzles.This can be easily verified by analyzing the results of comparative characteristics of the parameters of jets from different nozzles [15][16][17].These values with different turbulence coefficient (α) at a speed of at least 1.5 m/s at distances corresponding to the parameters of the experimental model of the roof are given in Table 2.For the experimental model, we chose an EVL 250/37 vortex blower with a capacity of 900 m 3 /h, compression 37 kPa, engine power 11 kW/h.When choosing the type, we took into account its obvious advantages of using it within the project: ensuring high productivity during normal operation of the equipment; the lowest noise level during operation in comparison with other devices, the compact shape, weight and dimensions facilitate the placement of the equipment in the attic of the roof of the building; sufficient degree of reliability: parts made of stamped aluminum are light and durable, maximum bearing life is 30,000 hours; versatility: can be used for both vacuum and compression, which can be useful when cleaning the route, absence of air pulsation and equipment vibration during operation, mobility and space saving: possibility of vertical installation in order to reduce pressure losses in the exhaust air duct; ease of maintenance, fire and explosion safety.(built-in safety anti-explosion valve), the ability to use a speed controller and connect automatic devices allows you to achieve an optimal combination of system efficiency and energy costs for equipment operation [18].
It was found that with an air flow rate per nozzle of 50 m 3 /h and a speed of 25 m/s at the nozzle exit, taking into account gravitational deflection is not required [19].
We calculated the number of nozzles per aerodynamic path, taking into account the parameters of the nozzle and blower: 18 pieces (6 on two slopes and 3 on two edges of the end part), the optimal distance between the nozzles is 65 cm [20,21].

Results of prototype design
Optimal nozzle options were created by injection molding from polymer materials using 3D models from Blender 3D and SolidWorks Flow Simulation.
An experimental roofing model, including a prototype, was made from a 3D model of the structure by cutting out the roof structure with real dimensions in order to reduce the overall dimensions of the model and to ensure its placement and maintenance during testing.A schematic diagram of the design of the experimental model is shown in Figure 1.A control system for the air supply unit was developed and installed, including manual, automatic and remote control systems, a monitoring and warning system.A schematic diagram of the control system is shown in Figure 2.

Test results of the prototype
Experimentally, to achieve the maximum result of the air flow speed on the section of the roof furthest from the nozzle, using hole plugs, we installed the optimal number of nozzles on the route -9 pieces.
From a large number of manufactured nozzles of various configurations, several variants of slot-shaped nozzles were selected experimentally using recalculation of air flow through outlet openings of different sizes, which showed significant parameters of the jet range -at least 2.0 m/s at the edge of the roof [21,22].The characteristics of these nozzles and the speed dynamics are shown in Table 3 and Figure 3.The results of testing the automatic system, remote control of the device, monitoring and warning system proved the clear operation of its basic functionality and service functions.Testing was carried out in August 2023, simulating snowfall with a snow generator.It turned out that it was impossible to provide conditions close to real operating conditions using artificial snow, as planned.Artificial snow flakes are foam formations of a surface-active liquid substance, the physical properties of which (density, wetting, specific volume, weight, surface tension, viscosity, compressibility) differ significantly from the properties of real falling snow.Simulating snowfall using a snow generator had mainly a demonstration effect.
The temperature factor during testing did not correspond to the operating conditions of the device in winter.At low temperatures, the density of air and snowflakes will be greater, which will ensure their greater elasticity and mobility.Testing conditions in the university's closed courtyard create turbulent air flows, preventing an objective assessment of the device's operation.The efficiency of blowing and the service area of the roofing device were assessed with a Testo 425 anemometer; air flow velocities were recorded in all areas along the roof perimeter from 2.0 to 4.0 m/s, which should ensure the blowing of snowflakes.The expected result can only be confirmed through operational tests in real climatic conditions.
Experimentally, during a period of intense snowfall (March 2023), it was found that on a flat surface (sheet of plywood) a layer of snow of 1 cm is formed in 15 minutes (according to the technical specifications, 3 cm is acceptable).Therefore, taking into account the possible need to create additional efforts to blow off snow that has already fallen onto the roof, the pause in the blower operation can be 15-20 minutes.
When testing temperature dynamics, it was found that after 30 minutes of engine operation, its surface temperature reaches 38 °C and does not increase further (operation of the blower ventilation system).Thus 38 °C is engine operating temperature.After turning off the engine for 10 minutes, the temperature rises to 52 °C and then a slow decrease in temperature (cooling) occurs -passive cooling.That is, you can turn on the engine 10 minutes after turning it off, when the temperature reaches 52 °C.Then, when the engine is turned on for 2 minutes, the engine temperature drops to operating temperature (38 °C) due to active cooling.The optimal timing mode for the installation has been set: "30 min pulse -10 min pause".
Checking the admissibility of noise indicators during equipment operation showed that the sound pressure level at a distance of 3 m from the part of the model covered by the roofing does not exceed the maximum permissible level value (MAL) for sales areas of stores, passenger areas of airports, train stations, reception centers of consumer service enterprises (equivalent sound level 60 dBA; maximum level 75 dBA -SanPIN 1.2.3685-21).At a distance of 3 m from the open part of the model, the noise level exceeds the permissible level by 9 dBA and amounts to 84 dBA.A sound level of 60 dBA was recorded at a distance of 20 m from the open part of the model.It should be noted that the testing conditions did not correspond to the actual operating conditions of the device -in a closed attic space that prevents the spread of noise, at a certain height from the area where people are present.If the noise levels measured during operation of the installation are exceeded, it is necessary to install a noise-insulating casing on the equipment, which reduces the noise by 8-10 dB, or to insulate the attic space with sound-absorbing material.The pressure created in the pipeline system is determined by the technical characteristics of the blower and does not exceed 37 kPa.This value complies with explosion safety requirements (Order of Rostechnadzor No. 536 dated December 15, 2020 N 536).The air temperature in the route after continuous operation of the device for 5 hours was 65 °C, which exceeds the maximum allowable limit for PVC pipes by 5 oC.During the "30x10" mode operation for 5 hours, the temperature did not exceed 40 °C, so the use of long-term uninterrupted operation of a device made of PVC pipes is not recommended.It is necessary to set the timing mode experimentally, or use pipes made of materials with a lower thermal conductivity coefficient for the manufacture of an aerodynamic route: polypropylene (upper limit of permissible operating temperatures +95 °C) or HDPE (+65 °C).In this case, it is necessary to take into account the relativity of the results obtained due to the fact that these tests were carried out at an ambient temperature of +22 °C.Under operating conditions on the roof in winter, the air temperature in the pipes will be significantly lower, then, perhaps, PVC pipes are suitable for long-term continuous operation.This must be verified during operational tests in winter.

Results of the developed technology
The technology involves the operation of a device that includes an aerodynamic path with nozzles, a vortex blower installed under the roof of the building to pump air into the aerodynamic path, which is driven by a precipitation sensor and a control unit.The system is equipped with a programmable device for operating modes of the blower in a given mode.The nozzles are adjusted during installation according to the angle of inclination of the roof and have a configuration that allows you to eliminate "blind" zones, ensuring the direction of the air flow parallel to the roof, blowing away precipitation while still "on approach".
Automatic prevention of snow accumulation on the roofs of buildings is carried out as follows.The precipitation sensor, recognizing the presence of precipitation, sends a signal to the control unit, which turns on the blower.The blower supplies air into a wind tunnel with nozzles installed on it, which allow it to serve the entire surface of the roof.The nozzles create flat jets of air parallel to the roof, blowing away snow as it falls, preventing it from accumulating on the roof surface.When precipitation stops, the precipitation sensor sends a signal to the control unit, which turns off the blower.The technology provides 3 control modes -automatic, remote, manual and a warning system about the correct operation of the equipment.Can be operated remotely by three operators simultaneously.
Recommendations for using the modes are given in Table 4.The technology is universal in terms of use on all pitched roofs.The aerodynamic path is mounted from unified standard parts, observing the calculated distance between the nozzles of 64-65 cm.The nozzles are made to order using injection molding from polymer materials.The optimal length of the route, taking into account the choice of equipment with the optimal weight, depending on the power, is about 5 m.For long roofs, instead of several blowers, it is advisable to divide the aerodynamic route into sections with intervals, each of which is combined by pipelines through a common manifold into one high-power blower.The collector is equipped with automatically switching shut-off devices (air valves), which in a given mode alternately redirect the entire air flow to the connected sections.Thus, alternately all sections of the route will service (blow) the entire roof without causing excessive energy consumption.For hip-type roofs, it is advisable to use a route with an exit from the center at a distance of 2/3 along each edge of the roof.
When designing a prototype of the device, we took into account the requirements of technical aesthetics -the entire route is covered with a protective metal canopy in the color of the roof and has a unique and universal, designed for all possible angular parameters of the slope, fastening design -simultaneously -the canopy and the route to the roof, minimizing the violation of the tightness of the coating.The canopy can be used for any pitched roof and helps preserve the aesthetics and architectural style of buildings.

Discussion
The developed control system when using technology on the roofs of all company buildings, which involves combining them into a common control panel, is not optimal.It is advisable to replace most of the discrete control elements (intermediate relays, time relays, precipitation sensor control unit, etc.), for example, with a programmable relay PR205 from the OWEN company.This will allow for more flexible configuration of equipment operating modes, and in combination with the PM210 network gateway (or PE210, PV210 depending on the required connection interface) and more flexible remote control and telemetry.If necessary, the system is easily expanded with PRM expansion modules from the same manufacturer.
From the point of view of the correct operation of the system, a big question is the logic of the precipitation sensor.In the future, it may make sense to reconsider the principle of precipitation detection in order to understand not only the presence, but also the intensity, and identify false alarms.This could be a combination of several sensors, not only precipitation, but also, for example, atmospheric pressure.An ultrasonic or optical sensor can detect snowflakes flying past, or install a camera.In this case, the programmable relay will no longer cope; it is necessary to use single-board computers such as Raspberry Pi.
Analyzing the results of a preliminary comparative assessment of all costs of using the technology and the costs of manual cleaning in terms of one year for one customer's roof, we can conclude:  The economic benefits from the massive widespread implementation of technology within even one railway company with the establishment of a single control center and the use of a high-tech automated complex, freeing a lot of workers from manual labor, eliminating risks and associated costs and payments, will obviously be more significant than from the use of manual labor.The introduction of technology on one roof involves suboptimal costs, which, as expected, will not show such benefits,  At this stage, it is premature to evaluate the economic effect; it is necessary to develop in detail and prove the practical effectiveness of factors for optimizing the technological parameters of the technology for roofs of different types and different climatic conditions: reducing the number and power of equipment through the use of automatic sequential switching of working routes on the same roof, optimization of monitoring systems precipitation,  The feasibility of introducing technology cannot be assessed only by economic benefits; it is necessary to take into account equally important aspects: preserving the life and health of people, eliminating manual labor; preservation of the building's architecture, aesthetics of the structure; the environmental contribution of technology, which excludes the use of natural resources, man-made impacts of chemicals, thermal pollution, without changing the laws of nature.

Conclusions
Analysis of the results of testing the developed technology for automatic prevention of snow accumulation on a roof model confirms the possibility of optimizing its parameters and the prospects for further research on its improvement and widespread use.These conclusions are due to the following technology capabilities:  The function of manual, remote and automatic control makes it possible to set the mode (work and pauses) depending on weather conditions, allows you to monitor the presence of precipitation (snow) and monitor the correct operation of equipment,  Allows you to prevent the accumulation of snow cover on the roofs of buildings with a layer of more than 30 mm, preventing the deposition of snow flakes on the roof, eliminating dangerous factors,  Automatic process control using modern precipitation control and automation tools will eliminate manual and dangerous labor,  The absence of moving structural elements results in a high degree of reliability and reduced costs for its maintenance and repair;  Elimination of mechanical factors affecting the roof when cleaning it helps to increase the wear resistance of roofs and save money on its repair;  Complete elimination of the risks of physical and psychophysiological labor factors for workers: falling from a height, injury from a mass of snow when it suddenly falls or is thrown from the roof; reducing the stress of the work process for managers, excluding liability for injury cases and the cost of permits to work at heights;  Allows you to save labor, time and financial resources: aspects of versatility for roofs of different sizes and types, unification of parts have been thought out;  It is environmentally and economically sound and safe;  The design of the device is covered with a universal protective canopy made of metal tiles in the color of the roof, without aesthetically changing the facades of the buildings,  The prospect of increasing efficiency and economy by optimizing technology parameters,  The prospect of widespread use of technology with a single control center using modern automation tools.
The research was carried out with the financial support of the Regional State Autonomous Organization "Krasnoyarsk Regional Fund for the Support of Scientific and Scientific-Technical Activities" and the Open Joint-Stock Company "Russian Railways" as part of the implementation of scientific project No. 2022101608895 "Development and design of remote control technology for clearing the roofs of buildings from snow" .

Fig. 2 .
Fig. 2. Structure diagram of the control system of the air supply unit.

Table 3 .
Characterization of optimal nozzles.
Distance from nozzle to roof slope edge, m

Table 1 .
Research Program.design of the Plant.Development of working design documentation.Formation of technical specifications for experimental design work.Manufacturing of the experimental unit according to the working drawings.Development of the program product.Preparation for testing of the experimental unit: installation, debugging (fine-tuning, model adjustment).Integration of the software product 6 Testing Verification Development of programs and methods of preliminary and acceptance tests.Testing of the Unit under conditions close to real conditions.Verification of research results, making changes to ensure the reliability of the unit.Approbation of the functional of the experimental sample.Feasibility study of design solutions and developed technology (safety, reliability, technology efficiency, environmental, economic, commercial feasibility).

Table 2 .
Comparative characterization of nozzles.

Table 4 .
Recommendations for using the modes.