An Innovative Falling Film Evaporative Cooling With Recirculation Driven by Low-Grade Heat

2009 ◽  
Vol 1 (4) ◽  
Author(s):  
S. He ◽  
R. Z. Wang ◽  
Z. Z. Xia ◽  
B. Tian ◽  
L. W. Wang
Keyword(s):  
Heat Transfer ◽  
Evaporative Cooling ◽  
Hot Water ◽  
Working Fluid ◽  
Small Scale ◽  
Inlet Temperature ◽  
Low Grade ◽  
Falling Film ◽  
Film Evaporator ◽  
Low Grade Heat

A falling film evaporator integrated with a recirculation tube driven by low-grade heat has been proposed to achieve a more compact and reliable system, which can be easily integrated into small-scale systems. An experimental study of the evaporative cooling of such an innovative falling film evaporator is presented. Water was used as the working fluid. The results are compared with published data for systems using mechanical pumps to circulate the fluid. Experimental investigation showed that the evaporative heat transfer coefficient of 6770–6870 W/m2 K can be achieved when the inlet temperature of the falling fluid is 29°C and the hot water entry temperature is 70°C. Detailed investigation on the effects of the driving heat source temperature and the inlet temperature of the hot water on the liquid film cooling mechanism was investigated. The results showed that for such a system, the effect of the falling film inlet temperature is more pronounced as compared with the other two parameters. Comparisons with traditional falling film evaporator with a mechanical pump indicated that the proposed integrated evaporator is more compact, reliable, and cost effective without impairing the heat transfer performance.

A Dual-Source Organic Rankine Cycle (DORC) for Improved Efficiency in Conversion of Dual Low- and Mid-Grade Heat Sources

2009 ◽  
Author(s):  
F. David Doty ◽  
Siddarth Shevgoor
Keyword(s):  
Heat Source ◽  
Heat Input ◽  
Temperature Limit ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Low Grade ◽  
Heat Sources ◽  
Reaction Products ◽  
Pinch Point ◽  
Low Grade Heat

Detailed thermodynamic and systems analyses show that a novel hybrid cycle, in which a low-grade (and low-cost) heat source (340 K to 460 K) provides the boiling enthalpy and some of the preheating while a mid-grade source (500 K to 800 K) provides the enthalpy for the final superheating, can achieve dramatic efficiency and cost advantages. Four of the more significant differences from prior bi-level cycles are that (1) only a single expander turbine (the most expensive component) is required, (2) condenser pressures are much higher, (3) the turbine inlet temperature (even with a low-grade geothermal source providing much of the energy) may be over 750 K, and (4) turbine size is reduced. The latent heat of vaporization of the working fluid and the differences in specific heats between the liquid and vapor phases make full optimization (approaching second-law limits) impossible with a single heat source. When two heat sources are utilized, this problem may be effectively solved — by essentially eliminating the pinch point. The final superheater temperature must also be increased, and novel methods have been investigated for increasing the allowable temperature limit of the working fluid by 200 to 350 K. The usable temperature limit of light alkanes may be dramatically increased by (1) accommodating hydrogen evolution from significant dehydrogenation; (2) periodically or continually removing undesired reaction products from the fluid; (3) minimizing the fraction of time the fluid spends at high temperatures. Detailed simulation results are presented for the case where (1) the low-grade heat source (such as geothermal) is 400 K and (2) the mid-grade Concentrated Solar Power (CSP) heat source is assumed to be 720 K. For an assumed condensing temperature of 305 K and working fluid flow rate of 100 kg/s, preliminary simulations give the following: (1) low-grade heat input is 25 MWT; (2) mid-grade heat input is 24 MWT; (3) the electrical output power is 13.5 MWE; and (4) the condenser rejection is only 35 MWT. For comparison, with a typical bi-level ORC generating similar power from this geothermal source alone, the low-grade heat requirement would be ∼100 MWT.

scholarly journals A Comparative Study of the Oil-Free Centrifugal Water Chillers with the Flooded or Falling Film Evaporator—A Case Study

Energies ◽  
2019 ◽  
Vol 12 (13) ◽  
pp. 2548
Author(s):  
Kuo-Shu Hung ◽  
Jenn-Chyi Chung ◽  
Chung-Che Liu ◽  
Jun-Jie Lin ◽  
Chi-Chuan Wang
Keyword(s):  
Heat Transfer ◽  
Comparative Study ◽  
Tube Bundle ◽  
Threshold Value ◽  
Working Fluid ◽  
Falling Film ◽  
Loading Test ◽  
Film Evaporator ◽  
Nominal Capacity ◽  
R 134A

A comparative study regarding the performance of real-scale oil-free centrifugal chillers having the flooded evaporator or falling film evaporator was conducted in this study. The nominal capacity for the test chillers was around 200~230 USRT (US refrigeration ton) (703~809 kW). The compressors of the two chillers were identical and R-134a was used as the working fluid. Both evaporators employed the same enhanced tubes (GEWA-B) to fulfill phase change. Tests were conducted in full, 75%, 50%, and 25% loading. Test results indicate that both chillers contained a comparable system performance with an integrated part-load value of around 8.62~8.63. The overall heat transfer coefficient for the flooded evaporator was appreciably higher (20~40%) than the falling film evaporator. This is because the falling film flowrate was below the threshold value and the heat transfer was dominated by evaporation mode. Yet, the heat transfer performance for the falling film evaporator was further jeopardized due to starvation of the film flowrate (partial dry-out), especially in the middle or bottom of the tube bundle. This phenomenon became even more pronounced at partial loading (25%), whereas the flooded evaporator did not reveal such a performance dip at partial loading.

Off-Design Performance Comparative Analysis Between Dual-Pressure Organic Rankine Cycles Using Pure and Mixture Working Fluids

2018 ◽  
Author(s):  
Yang Du ◽  
Ying Long ◽  
Muting Hao ◽  
Yaowu Huo ◽  
Pan Zhao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mass Fraction ◽  
Hot Water ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Heat Transfer Area ◽  
Water Parameters ◽  
Design Performance ◽  
Pressure Pump ◽  
Organic Rankine Cycles

Dual-pressure Organic Rankine Cycles (ORCs) driven by the low temperature heat source usually work under part-load conditions, and it is therefore essential to predict the off-design performance of such ORCs. This paper presents the off-design performance prediction of the dual-pressure ORC on the basis of the model including plate heat exchangers, axial turbines and a centrifugal pump. Pure working fluid R600a and the mixture R245fa/R600a are compared. The sliding pressure operation strategy is considered under off-design conditions. The results indicate that under the design hot water parameters (hot water 140 °C, 64.87 kg/s), compared with the single-pressure ORC using R600a, the dual-pressure ORC using R600a shows a 9.57% higher net power and a 17.32% higher heat transfer area. Furthermore, the dual-pressure ORC with the mixture R245fa/R600a (0.42/0.58 mass fraction) shows a 1.04% higher net power and a 3.87% higher heat transfer area than the dual-pressure ORC using R600a under the design hot water parameters. In the dual-pressure ORC, the rotational speed of the high-pressure pump is more strongly influenced by the inlet temperature of hot water than that of the low-pressure pump. In addition, when the mass flow rate ratio of hot water or the inlet temperature of hot water increases, the difference of the net power between the dual-pressure ORC using the proposed mixture R245fa/R600a (0.42/0.58 mass fraction) and that using pure R600a increases.

Working Fluid Dependence on Source Temperature for Organic Rankine Cycles

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Hugo Darío Pasinato
Keyword(s):  
Performance Indicator ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Low Grade ◽  
Working Fluids ◽  
Source Temperature ◽  
Operation Conditions ◽  
Organic Rankine Cycles ◽  
Low Grade Heat ◽  
Selection Of

Abstract This paper presents the results of numerical simulations of organic Rankine cycles (ORCs) for low-grade heat source temperature in the range of 373–653 K for 20 working fluids. The goal of the study is to determine the importance of the level of the source temperature in the selection of working fluids and operation conditions. As a performance indicator, a function of the net power, the internal and external exergy efficiencies, and the exergy efficiency of the evaporator is used. The results show that there is a strong correlation between the level of the source temperature and the critical temperature, between the expander inlet temperature and the source temperature, and between the expander inlet pressure and the critical pressure of the working fluids tested. The study shows that once the source temperature level is known, it is possible to select the working fluid and the conditions at the expander entrance.

Experimental Implementation of a Micro-Scale ORC-Based CHP Energy System for Domestic Applications

2010 ◽  
Author(s):  
Massimo Malavolta ◽  
Asfaw Beyene ◽  
Mauro Venturini
Keyword(s):  
Low Temperature ◽  
Heat Source ◽  
Hot Water ◽  
Economic Viability ◽  
Small Scale ◽  
Low Grade ◽  
Micro Scale ◽  
Exhaust Heat ◽  
Domestic Use ◽  
Low Grade Heat

Because of the renewed interest in renewable energy as well as increased emphasis on alternative technologies, micropower-generating systems have attracted considerable research interest over the last decade. However, micro-scale power generation for low grade heat recovery applications, i.e. as low as 1–3 kW - for domestic use, are characterized by very low efficiencies and relatively high specific cost. For economic viability, these factors make it imperative that the heat source remains “free”, such as solar or geothermal energy. In this paper, a small-scale Organic Rankine Cycle (ORC) is presented. The small-scale ORC module was built and tested at San Diego State University lab, aimed at producing electricity and hot water from ultra-low grade heat source that can be tapped from solar collectors and low temperature exhaust heat. The system was built for economic viability and flexibility, tailored for a domestic use. The tests demonstrated that the system offered CHP capability, with electric and thermal power output suitable for a domestic application. It also offered high operational flexibility, since the scroll expander could work with a high temperature range, accommodating an even-significant drop of the heat source temperature. Therefore, it can be conveniently used to capture solar and low-temperature energy sources. The system could be produced at an overall cost of less than $3,000 (USD 2010).

Feasibility Study of Ammonia-Water Vapor Absorption Heat Transformer

1987 ◽  
Vol 109 (2) ◽  
pp. 96-100 ◽  
Author(s):  
A. Ertas ◽  
P. Gandhidasan ◽  
J. J. Luthan
Keyword(s):  
Operating Conditions ◽  
Hot Water ◽  
Working Fluid ◽  
Low Grade ◽  
Water Vapor Absorption ◽  
Industrial Sectors ◽  
Permissible Range ◽  
Vapor Absorption ◽  
Low Grade Heat ◽  
Heat Transformer

Many industrial sectors reject heat to the atmosphere in the form of hot water with a temperature between 40° and 70°C. This low grade heat can be upgraded by using a vapor absorption heat transformer (AHT). The present study considers a single stage AHT with binary mixture of NH3–H2O as the working fluid. The performance characteristics of the system have been evaluated by solving the governing mass and energy balance equations using a digital computer. It is found that the permissible range of concentration across the absorber is 0.04<ΔX<0.075 for the following operating conditions: Tusefulheat≤120°C,43°≤Twasteheat≤88°Cand10°≤Tsink≤27°C.

1-D Model Analysis of Tesla Turbine for Small Scale Organic Rankine Cycle (ORC) System

2017 ◽  
Author(s):  
Jian Song ◽  
Chun-wei Gu
Keyword(s):  
Large Scale ◽  
Low Cost ◽  
Organic Rankine Cycle ◽  
Axial Flow ◽  
Rankine Cycle ◽  
Expansion Ratio ◽  
Working Fluid ◽  
Small Scale ◽  
Low Grade ◽  
D Model

Energy shortage and environmental deterioration are two crucial issues that the developing world has to face. In order to solve these problems, conversion of low grade energy is attracting broad attention. Among all of the existing technologies, Organic Rankine Cycle (ORC) has been proven to be one of the most effective methods for the utilization of low grade heat sources. Turbine is a key component in ORC system and it plays an important role in system performance. Traditional turbine expanders, the axial flow turbine and the radial inflow turbine are typically selected in large scale ORC systems. However, in small and micro scale systems, traditional turbine expanders are not suitable due to large flow loss and high rotation speed. In this case, Tesla turbine allows a low-cost and reliable design for the organic expander that could be an attractive option for small scale ORC systems. A 1-D model of Tesla turbine is presented in this paper, which mainly focuses on the flow characteristics and the momentum transfer. This study improves the 1-D model, taking the nozzle limit expansion ratio into consideration, which is related to the installation angle of the nozzle and the specific heat ratio of the working fluid. The improved model is used to analyze Tesla turbine performance and predict turbine efficiency. Thermodynamic analysis is conducted for a small scale ORC system. The simulation results reveal that the ORC system can generate a considerable net power output. Therefore, Tesla turbine can be regarded as a potential choice to be applied in small scale ORC systems.

scholarly journals Thermal Characteristics Analysis on Multi- Heat Pipe Induced Heat Exchanger

2019 ◽  
Vol 9 (2S2) ◽  
pp. 143-147 ◽  
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Pipe ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Cold Water ◽  
Hot Water ◽  
Working Fluid ◽  
Physical Parameters

In this investigation of multi heat pipe induced in heat exchanger shows the developments in heat transfer is to improve the efficiency of heat exchangers. Water is used as a heat transfer fluid and acetone is used as a working fluid. Rotameter is set to measure the flow rate of cold water and hot water. To maintain the parameter as experimental setup. Then set the mass flow rate of hot water as 40 LPH, 60LPH, 80 LPH, 100LPH, 120 LPH and mass flow rate of cold water as 20 LPH, 30 LPH, 40 LPH, 50 LPH, and 60 LPH. Then 40 C, 45 ºC, 50 ºC, 55 C, 60 ºC are the temperatures of hot water at inlet are maintained. To find some various physical parameters of Qc , hc , Re ,, Pr , Rth. The maximum effectiveness of the investigation obtained from condition of Thi 60 C, Tci 32 C and 100 LPH mhi, 60 LPH mci the maximum effectiveness attained as 57.25. Then the mhi as 100 LPH, mci as 60 LPH and Thi at 40 C as 37.6%. It shows the effectiveness get increased about 34.3 to the maximum conditions.

scholarly journals Thermal Analysis of the Effects of Multifaceted Conditions on Performance of Shell-and-Tube Heat Exchanger

2021 ◽  
Vol 6 (1) ◽  
pp. 69-75
Author(s):  
Taiwo O. Oni ◽  
Ayotunde A. Ojo ◽  
Daniel C. Uguru-Okorie ◽  
David O. Akindele
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Parallel Flow ◽  
Hot Water ◽  
Inlet Temperature ◽  
Fiber Glass ◽  
Counter Flow ◽  
Tube Heat Exchanger ◽  
Shell And Tube ◽  
Flow Configurations

A shell-and-tube heat exchanger which was subjected to different flow configurations, viz. counter flow, and parallel flow, was investigated. Each of the flow configurations was operated under two different conditions of the shell, that is, an uninsulated shell and a shell insulated with fiber glass. The hot water inlet temperature of the tube was reduced gradually from 60 oC to 40 oC, and performance evaluation of the heat exchanger was carried out. It was found that for the uninsulated shell, the heat transfer effectiveness for hot water inlet temperature of 60, 55, 50, 45, and 40 oC are 0.243, 0.244, 0.240, 0.240, and 0.247, respectively, for the parallel flow arrangement. For the counter flow arrangement, the heat transfer effectiveness for the uninsulated shell are 2.40, 2.74, 5.00, 4.17, and 2.70%, respectively, higher than those for the parallel flow. The heat exchanger’s heat transfer effectiveness with fiber-glass-insulated shell for the parallel flow condition with tube hot water inlet temperatures of 60, 55, 50, 45, and 40 oC are 0.223, 0.226, 0.220, 0.225, and 0.227, respectively, whereas the counter flow condition has its heat transfer effectiveness increased by 1.28, 1.47, 1.82, 1.11, and 1.18%, respectively, over those of the parallel flow.

scholarly journals Small Scale Power Generation using Low Grade Heat from Solar Pond

2012 ◽  
Vol 49 ◽  
pp. 50-56 ◽  
Author(s):  
Baljit Singh ◽  
J. Gomes ◽  
Lippong Tan ◽  
Abhijit Date ◽  
A. Akbarzadeh
Keyword(s):  
Power Generation ◽  
Small Scale ◽  
Low Grade ◽  
Solar Pond ◽  
Low Grade Heat
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