N. Sedaghat Herfeh; A. M. Nikbakht; H. Mobli; A. R. Keyhani; A. Piri
Abstract
IntroductionSour cherry concentration is a significant agro-industry in the world. In 2016, world production was 13.8 million tons and most of which were processed in the form of concentrate or frozen products. Iran has the 6th rank among the producers of sour cherry and experienced a highly rise (45%) ...
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IntroductionSour cherry concentration is a significant agro-industry in the world. In 2016, world production was 13.8 million tons and most of which were processed in the form of concentrate or frozen products. Iran has the 6th rank among the producers of sour cherry and experienced a highly rise (45%) in production in 2016. A conventional energy system evaluation is performed using the energy analysis method. The thermodynamic inefficiencies occurring within the system (factors that cause a gap between performance and ideal state) are not identified and evaluated by energy analysis.Materials and MethodsPakdis concentrate production line includes a plate heat exchanger (HE) converter to preheat input juice using condensate water energy and crude juice heat outlet, four multipurpose falling evaporators (E1, E2, E3, E4), a distillation tower for raw juice aromatization (DT) and a juice cooling system (JC).A thermographic camera (G120EXD, NEC Avio, Japan) was used for thermographic recording. Initial examination of the thermography results showed that the external surface temperature of the equipment except for the evaporators (E1, E2, E3, E4), the boilers (B1, B2, B3) and the condensation tank of the evaporation line (CT1) had very little difference with the ambient temperature around them, and therefore, their heat flux was ignored.Due to limitations, the mass flow rates of the evaporation line (except for inlet juice) were not measurable, and therefore, energy analysis was used to calculate them. Energy analysis involves the simultaneous resolution of mass and energy balances for a system.Results and DiscussionThe heat loss rate from the first evaporator (E1) was calculated to be 21.23 kW from which mass/energy balances and mass flows were extracted. Also, heat loss rate from utilities E2, E3, E4, and CT1 were calculated from mass-energy balances. Streams 32, 49, 52, and 54 are not utilized and exit the system. Hence, they are assigned as heat loss streams within the evaporation line.The total energy loss rate in the evaporation line was calculated to be 4920.82 kW which contributes 74.8% of total input energy to the line. However, 73.39% of this loss is assigned to the cooling tower (stream 54). Stream 29 from the 4th stage evaporator enters the condenser, mixes with water, and provides cold water goes to the cooling tower. In the tower, water evaporates and dissipates heat to the environment. Stream 32 is the second loss stream with 14.8%. Also, it should be noted that heat loss from the surface of utilities makes 3.06% of energy loss of the evaporation line which implies that insulations are done properly in utilities.Evaporation performance may be rated simply and primarily by the steam economy. The value was calculated to be 2.63 in the evaporation line, i.e. 2.63 kg water is evaporated per 1 kg steam injected into the systemExergy rate in several streams of evaporation line. The exergy rate of fuel and products, exergy efficiency, exergy destruction rate, and exergy destruction ratio for each element of the line were reported. Total input exergy to the evaporation line is 4832.03 kW from which 1045.85 kW is destructed due to irreversibility and 3786.19 kW is dissipated.Major destruction occurs within barometric condenser (BC), pressure reducing valve (PR), a plate heat exchanger (HE), evaporators 1 and 2 (E1 and E2), cooling tower (CT), and then evaporators 3 and 4 (E3 and E4). The remaining destruction in other utilities is negligible.ConclusionUsing the first and second laws of thermodynamics and instrumentation procedure, sub-systems of the evaporation unit of Pakdis Company were investigated and energy and exergy balances were coupled and solved. Thermographic assessment of likely zones to energy losses was employed. The whole process was monitored and mass-energy balances were developed. The steam economy as a reliable criterion for evaporation was calculated. To extract inefficiencies and possible optimizable unit operations exergetic analyses were carried out and subsequently the share of exergy loss and destruction and capital cost in the whole process was defined. It was found that capital cost is consistently ignorable compared to exergetic faults such as losses and destructions.
