## 1 Introduction  
Particulate matter emissions released into the environment from thermal decomposition of fuel because of human activity are currently one of the most serious environmental burdens. PM particles from combustion, reaching a size of only a few micrometers, are easily carried into the environment together with the flue gases, where they can be inhaled by living organisms with risks of development of lung diseases [1]. The main source of PM emissions is the combustion of solid fuels in small heat sources, the number of which is constantly growing. This trend is also increased by the promotion of biomass as a renewable resource, which is becoming the preferred alternative to cleaner but more expensive fossil natural gas. In addition to promoting green energy from biomass, the European Union's policy also aims to reduce emissions from combustion devices that are constantly innovated to reach new standards. This effort of design modifications on the combustion devices significantly reduces their emissivity while guaranteeing optimal combustion conditions. Evidence of this is one Chinese research report that shows a 76% reduction in PM emissions by design improvements to traditional coal stoves. There was a reduction of up to 95% while using a modern gasification boiler [2]. Further research has shown a significant reduction in emissions by ensuring optimal combustion conditions using separation baffles and combustion air distribution [3]. However, these design modifications in combustion devices reach the limits of technical possibilities and it is therefore necessary to focus on technologies of secondary separation of already formed particles by using mechanical, electrostatic, or filtration separators as it is in large heat sources. Initial research was focused on the use of mechanical chamber separators using centrifugal, gravitational, or inertial force to reduce the velocity of the carried particle below the rate of fall [4; 5]. One study examined the use of a chamber separator with adjustable separation blades. By rotating the blades, it was possible to influence the magnitude of the forces affecting the velocity of the particle. Measurements showed that the largest particles did not pass through the first blade section. Of the total number of particles, 55.17% were captured. However, despite the entrapment of larger particles, smaller particles escaped in the flue gas stream [6]. Despite the widespread use of mechanical separators, the main part of research is currently focused on the use of electrostatic precipitators, which are preferred due to their simple installation with low space requirements, high efficiency, and low cost. The wider use of electrostatic precipitators has been facilitated by the reduction in the cost of manufacturing high-voltage transformers, which are among the more expensive components of the separator. The separation effect is achieved by creating a high voltage potential between the positive and negative electrodes between which the entrained flue particles pass. The particles are charged by ion current from the discharge electrode and are attracted to collection grounded electrode. Most electrostatic precipitators use chimney pipes directly as collection electrodes, with a charging wire electrode stretched in the middle. Much research has already been applied to conventional chimney electrostatic precipitators and some models are currently available on the market [7; 8; 9; 10; 11]. Most research confirms the low efficiency of standard chimney separators and therefore some focus on their design improvement is necessary to increase the efficiency of particle separation [12; 13; 14; 15]. From a survey of the conducted research, the most inspiring models for us were multiple tubular separators, such as the Thai model, which achieved an efficiency of up to 70% [16; 17; 18]. The aim of this work was to continue this research and build an improved model of the standard chimney separator by multiplying the number of pipes.