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Management of domestic hot water system based on the example of a gas-fired instantaneous water heater

Jachimowski Artur, Pełka Grzegorz, Luboń Wojciech, Folta Michał

Zeszyty Naukowe. Organizacja i Zarządzanie / Politechnika Śląska

2024

z. 194

95--111

Purpose: The aim of the study was to present the actual efficiency of a gas-fired instantaneous water heater for the production of domestic hot water. Design/methodology/approach: The object of the study was a gas-fired instantaneous domestic hot water heater located in a flat in Krakow. Measurements with a suitable device were carried out for three basic variants of hot water preparation, defined as showering, washing hands and washing dishes. Findings: The tests and analyses carried out have revealed that the current efficiency (average efficiency based on 3 measurements - 77.61%) differs radically from that indicated on the water heater data sheet. Such a drop in efficiency may be caused e.g. by fouling of the surface of the heat exchanger on the flue gas side and scaling of the exchanger on the heated side. Research limitations/implications: The tests proved that the heater did not reach its nominal efficiency during the tests, but on the other hand, simulations of different intensities and durations of water consumption did not drastically change the efficiency of hot water preparation. Practical implications: Regular cleaning of the exchanger would probably reduce the difference between the efficiency declared by the manufacturer and the one achieved during the tests. A clean heater will also ensure a sufficiently low level of carbon monoxide in the flue gas, which has a real impact on the safety of the appliance. Social implications: The values obtained from the measurements for each operating mode can help occupants understand how to prepare water most efficiently with this particular appliance, which will have a real impact on the bills they pay. The user will be provided with information on what percentage of energy they use from the volume of gas burned. Originality/value: Gas-fired instantaneous water heaters provide an efficient and energysaving solution, especially in situations where the demand for hot water is low, and immediate access to it is crucial.

Numerical studies of plasma edge in W7-X with 3D FINDIF code

Jabłczyńska Małgorzata, Pełka Grzegorz, Jakubowski Marcin, Ślęczka Marcin

Nukleonika

2023

Vol. 68, No. 4

83--90

Modelling of the plasma transport for inherently three-dimensional (3D) problems as in stellarators requires dedicated complex codes. FINDIF is a 3D multifl uid plasma edge transport code that has been previously successfully used for the analysis of energy transport in the TEXTOR-DED tokamak [1], where 3D perturbations led to an ergodic structure of fi eld lines in the plasma edge. The ongoing efforts to apply it meaningfully to Wendelstein 7-X (W7-X) plasma problems resulted in advancements in the main model and accompanying tools for mesh generation and post-processing. In order to verify the applicability of the code and to compare with the reported simulation (EMC3-EIRENE) and experimental (OP1.1) results, a series of simulations for varying plasma density, temperature and anomalous transport coeffi cients as well as for fi xed input power were performed. The connection length pattern of FINDIF traced magnetic fi eld lines on the limiter was reproduced and its impact on heat loads was confi rmed. An increase in the peak heat load on the limiter with a rise in plasma density, temperature and anomalous plasma transport coeffi cients was observed. The decay lengths of density, electron temperature and heat fl ux did not change with density, and were decreasing with temperature and increasing with anomalous plasma transport coeffi cient, which was compared to the simple scrape-off layer (SOL) model.