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Simplified exergy analysis of ship heating systems with different heat carriers and with the recovery of waste heat

Zeńczak Wojciech

Archives of Thermodynamics

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2019

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Vol. 40, no 3

211-228

EN

The application of waste heat from exhaust gas of ship’s main engines has become widely practiced as early as in the 1930s. Thus the increase of ship’s overall efficiency was improved. Nowadays all newly built ships of the 400 gross tonnage and above must have specified energy efficiency design index, which is a measure for CO2 emissions of the ship and its impact on the environment. Therefore, the design of waste heat recovery systems requires special attention. The use of these systems is one of the basic ways to reduce CO2 emissions and to improve the ship’s energy efficiency. The paper describes the ship’s heating systems designed for the use of waste heat contained in the exhaust gas of self-ignition engines, in which the heat carriers are respectively water vapor, water or thermal oil. Selected results of comparative exergy analysis of simplified steam, water and oil heating systems have been presented. The results indicate that the oil heating system is comparable to the water system in terms of internal exergy losses. However, larger losses of exergy occur in the case of a steam system. In the steam system, a significant loss is caused by the need to cool the condensate to avoid cavitation in boiler feed pumps. This loss can in many cases cause the negative heat balance of ship during sea voyage while using only the exhaust gas boilers.

2

Methodology of calculation of multiplex heat exchang apparatus with cross flow and mixing in heat carriers

Ganzha A. M., Zaiets O. M., Marchenko N. A., Kollarov O. J., Njemcev E. M.

Journal of New Technologies in Environmental Science

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2018

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Vol. 2, nr 1

26--35

EN

The most efficient apparatus are known to be heat exchangers with classic countercurrent flow of heat carriers. However, this current scheme is rarely possible to create in an apparatus. In many cases cross flow heat exchangers are more acceptable in terms of efficiency of heat emission from the outer surface of the wall. Therefore cross flow if used which is within the identical surface area and heat-transfer rate in disadvantage in comparison with the classic countercurrent scheme. In this case multiple passes mixed diagram are mainly used where with sufficient number of cross flow passes reciprocal flow of heat carriers is close to the classic countercurrent. The most widespread assembling design of heat exchangers is complex and mixed current design. Unlike the simple mixed design one of the heat carriers moves as split flow lines through the full length and it does not interfuse between the passes and a heat carrier, which is inside as a rule within one pass and flows as split flow lines and it interfuses between the passes. In such a way the design of the mixed flow will be complex where every pass (section) is a complex cross flow diagram. Heat exchangers that are under analysis are widely spread in the different fields of the economy. That is why receiving more accurate and perfect methods and techniques of their research and analysis is an urgent task.

3

Paliwa stałe oraz przyszłość kotłów stałopalnych małej mocy

Ojczyk G.

Ciepłownictwo, Ogrzewnictwo, Wentylacja

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2016

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T. 47, nr 2

55--60

PL

Omówiono scentralizowane (zdalaczynne) oraz rozproszone (zdecentralizowane) systemy źródeł ciepła do ogrzewania i przygotowania c.w.u. Przeanalizowano względy ekonomiczne stosowania kotłów opalanych różnego rodzaju paliwami, jak też dostępność tych paliw i ich koszt jednostkowy. Przedstawiono kierunek rozwoju stałopalnych kotłów dwufunkcyjnych. W związku z rosnącymi wymaganiami w odniesieniu do efektywności kotłów, czystości spalin oraz komfortu użytkowania urządzeń grzewczych istniejące kotły stałopalne na węgiel kamienny są i będą poddawane badaniom przy spalaniu pelletu jako paliwa zastępczego.

EN

Centralized (district heating) and distributed (decentralized) heat source systems are discussed for heating and preparation of domestic hot water. Economic aspects of the use of boilers fired by fuels of various type have been analysed, as well as the availability of the fuels and their cost per unit. The direction of development of bifunctional boilers has been shown. With growing demands in terais of boiler efficiency, exhaust emissions, and comfort of use, existing hard coal boilers will be tested when burning pellets as an alternative fuel.

4

Simulating heat-transfer processes in two-phase heat-utilizer at heat pipes

Kulikova N., Redko A.

Structure and Environment

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2014

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Vol. 6, no. 2

35--43

EN

The choice of rational heat-utilizer heating scheme is a very current problem of energy saving when using boiler units. This article proposes the heat computation technique of heat exchanger at heat pipes with deep combustion - product cooling in boilers and water steam condensation. In addition, the construction scheme of heat exchanger made with two units in which the heat pipes are filled with different working medium is described. The numerical study results of heat carrier temperature and pressure distribution, namely: combustion products and water being heated according to counterflow - heat exchanger length are presented. The efficiency of two-phase heat-utilizer is determined.