Energy and exergy analyses of natural gas-fired boilers in a district heating system

Terhan, Meryem; Çomaklı, Kemal

doi:10.1016/j.applthermaleng.2017.04.091

Cited by 69 publications

(24 citation statements)

References 11 publications

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“…Table 2 shows the relation between the SPF of a water-water heat pump and the return temperatures at the consumer base (secondary side). The rate of exergy input of the gas-boiler booster is defined by using the exergy efficiency of a gas-fired boiler with the value of 0.328, as proposed by Terhan et al [20]:…”

Section: Exergy-analysis Modelmentioning

confidence: 99%

Exergy Analyses of Low-Temperature District Heating Systems With Different Sanitary Hot-Water Boosters

Poredoš

Kitanovski

Poredoš³

2019

Entropy

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This paper presents an exergy-efficiency analysis of low-temperature district heating systems (DHSs) with different sanitary hot-water (SHW) boosters. The required temperature of the sanitary hot water (SHW) was set to 50 °C. The main objective of this study was to compare the exergy efficiencies of a DHS without a booster to DHSs with three different types of boosters, i.e., electric-, gas-boiler- and heat-pump-based, during the winter and summer seasons. To achieve this, we developed a generalized model for the calculation of the exergy efficiency of a DHS with or without the booster. The results show that during the winter season, for a very low relative share of SHW production, the DHS without the booster exhibits favorable exergy efficiencies compared to the DHSs with boosters. By increasing this share, an intersection point above 45 °C for the supply temperatures, at which the higher exergy efficiency of a DHS with a booster prevails, can be identified. In the summer season the results show that a DHS without a booster at a supply temperature above 70 °C achieves lower exergy efficiencies compared to DHSs with boosters at supply temperatures above 40 °C. The results also show that ultra-low supply and return temperatures should be avoided for the DHSs with boosters, due to higher rates of entropy generation.

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Section: Exergy-analysis Modelmentioning

confidence: 99%

Exergy Analyses of Low-Temperature District Heating Systems With Different Sanitary Hot-Water Boosters

Poredoš

Kitanovski

Poredoš³

2019

Entropy

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“…Here, α refers to the amount of excess air and λ refers to the excess air ratio [32]. The excess air ratio for natural gas combustion is normally in the ranges of 1.05-1.2 [32][33][34][35]. The excess air ratio is set as 1.2 in this study.…”

Section: Gas Burnermentioning

confidence: 99%

Investigation of a gas-fuelled water heater based on combined power and heat pump cycles

Liang

Al-Tameemi

2018

Applied Energy

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In this paper, we proposed and demonstrated a novel gas-fuelled hot water system based on combined power and heat pump cycles. It essentially integrates a premixed gas burner, an organic Rankine cycle (ORC) power plant, and an air source heat pump for supplying hot water. An ORC power plant generates mechanical power from the thermal energy produced from the combustion of natural gas in the burner. Subsequently, the generated power directly drives a vapour compression cycle heat pump through a common shaft connecting the expander and the compressor. Cold tap water is headed firstly in the condenser of the heat pump, then in the condenser of the ORC power plant, and finally the flue gas exiting from the burner in a post heater. The flue gas exiting the post heater will be mixed with ambient air to further extract its residual heat in the evaporator of the heat pump. The advantages of the proposed system are threefold. First, the waste heat of the power cycle has been fully recovered. Second, the heat pump operates on a much lower temperature difference, leading to 2 higher COP. Third, it has no electrical generator or motor, avoiding the transduction losses. A comprehensive analysis has been presented in this paper, and the results show that the proposed system can achieve an overall fuel-to-heat efficiency up to 147% when the cold water is heated from 10 to 65 °C and the ambient air temperature is in the range-5 to 5 °C. The research results demonstrated that the proposed technology has a great potential for hot water applications.

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“…Results showed that the boiler and solar tower have minimum exergy performances that together the exergy losses of these two components constitute 85% of the total exergy losses of all components. In 2017, Terhan and Comakli studied energy and exergy analysis of boilers with gas as fuel. They found out that, the part with the most irreversibility in boilers is the combustion chamber.…”

Section: Introductionmentioning

confidence: 99%

Exergy analysis of a hybrid solar‐fossil fuel power plant

Vakilabadi

Bidi

Najafi

et al. 2019

Energy Science & Engineering

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In this study, exergy analysis, energy analysis, and mathematical modeling are performed in a 35 MW solar‐fossil fuel power plant. The losses of exergy and energy in different components and also changes of the efficiency of exergy and energy are analyzed at a specific day, 20th June. The assumed power plant in this study is Solar Electric Generating Station VI (SEGS VI), located in California's Mojave Desert. A parametric study, under different working conditions, including different working pressures, temperatures, collector output temperature, steam flow rate, and heat transfer fluid (HTF) flow rate is studied and the effect of variation of parameters on the performance of the plant is investigated. Authors found that, the maximum exergy loss happens in the collector and the maximum energy loss occurs in the condenser. Energy analysis shows that 47% of the total loss energy in the cycle happens in the condenser, as the main component that wastes energy. From exergy analysis, the collector and then boiler are the main components wasting exergy where 68.32% of total exergy loss occurs in these two components in hybrid mode (solar‐fossil fuel). Exergy and Energy efficiency variations throughout the day show that minimum exergy efficiency (32.7%) and maximum energy efficiency (23%) occurs at 12 am. Exergy efficiency variation versus turbine inlet pressure shows that the maximum exergy efficiency (26%) accure at 95 bar. The changes of the absorbed heat and solar irradiation of the 20th of June shows a good agreement with the measured data in validated reference.

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Energy and exergy analyses of natural gas-fired boilers in a district heating system

Cited by 69 publications

References 11 publications

Exergy Analyses of Low-Temperature District Heating Systems With Different Sanitary Hot-Water Boosters

Exergy Analyses of Low-Temperature District Heating Systems With Different Sanitary Hot-Water Boosters

Investigation of a gas-fuelled water heater based on combined power and heat pump cycles

Exergy analysis of a hybrid solar‐fossil fuel power plant

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