Investment casting is one of the precise casting methods where disposable wax patterns made in wax injection molds are used to make a casting mold. The production capacity of precision foundry is determined by the time taken for producing wax patterns, which depends on the time taken for wax solidification. Wax injection molds are usually made of aluminum or copper alloys with the use of expensive and time-consuming computer numerical control (CNC) processing, which makes low-volume production unprofitable. To reduce these costs, the authors present a heat transfer analysis of a 3D printed wax injection mold. Due to the low thermal conductivity of the photopolymer resin, the influence of different cooling channels’ shapes was investigated to improve the time of the manufacturing process. Transient thermal analysis was performed using COMSOL software based on the finite element method (FEM) and included a simulation of wax injection mold cooling with cold air (−23 °C), water, and without cooling. The analysis showed that use of cooling channels in the case of photopolymer material significantly reduces the solidification time of the sample (about 10 s shorter), and that under certain conditions, it is possible to obtain better cooling than obtained with the aluminum reference wax injection mold (after approximately 25–30 s). This approach allows to reduce the production costs of low-volume castings.

The aim of the experimental research was to determine the impact of changes in the air-fuel equivalence ratio during the combustion of wood pellet in the boiler on CO and NOX emissions. To realize the tests was used the 10 kW wood pellet boiler equipped with a dedicated wood pellet burner. Based...

This article presents a thorough analysis of the main reasons behind the generation of nitrogen oxides (NO_x) during combustion of coal-derived fuels in low- and medium-power boilers. Tests were made based on data from real-exiting heating systems operating in Poland over the last three years. Results of analytical research were used to conduct original experimental tests indicating the main problems of scattered municipal power engineering in Poland.

The paper presents experimental results for an axisymmetrical jet flow impinging with outflow through a reverse chamber. The test results include the average distributions and fluctuations of pressures on the impinged wall and the side wall of the chamber. The presented results cover further the mean velocities and the velocity fluctuations in the reverse chamber in relation to two velocity components: axial and radial. The purpose of the paper is to indicate the differences between different flow situations: the axisymmetrical free jet, the impinging jet hitting a flat surface, and a flow geometrically alike, however, restricted in outflow through a reverse annular chamber.

The aim of this paper is to present the design and working principle of a portable testing device for heat pumps in the energy recirculation system. The presented test stand can be used for any refrigerating/reverse flow cycle device to calculate the device energy balance. The equipment is made of two portable containers of the capacity of 250 liters to simulate the air heat source and ground heat source with a system of temperature stabilization, compressor heat pump of the coefficient of performance (COP) of = 4.3, a failsafe system and a control and measurement system.