Efficiency and losses analysis of low-pressure feed water heater in steam propulsion system during ship maneuvering period

Dominant propulsion systems of today’s LNG carriers are steam propulsion systems. Although a number of alternatives are developed, only steam propulsion systems in LNG carriers can fulfill a double function: the function of propulsion and on the other side the combustion of large amounts of BOG (Boil Off Gas) in one or more steam generators. In this paper was provided an analysis of the low-pressure feed water heater, as one of the important components of LNG carrier steam propulsion system. Based on the measured data for all flowing substances throughout the low-pressure feed water heater, it was performed numerical analysis of his energy and exergy efficiency, as well as calculation of energetic and exergetic power losses. The measurements were performed during LNG carrier maneuvering period, what enables insight into the operating parameters of heat exchanger during partial loads of steam propulsion system. From the energetic point of view the low-pressure feed water heater is a nearly perfect balanced device. Analyzed heat exchanger noticeable problems can be seen in exergy efficiency and exergy losses. Exergy represent the maximum available energy potential of any observed component in relation to the environment state. Impact of ambient temperature on the size of the exergy losses has been investigated at the end of conducted analysis. The low-pressure feed water heater is an example of a device which is very well balanced on the one side, even in the conditions of the steam system partial loads, and on the other side his available exergy potential is very poorly exploited

Energy and Exergy Efficiency Analysis of Sealing Steam Condenser in Propulsion System of LNG Carrier

In ship propulsion systems today diesel engines are dominant, but steam propulsion systems prevail in one type of ships and that are LNG carriers. Such steam propulsion systems consist of many different components. One interesting component of these systems is sealing steam condenser analysed in this paper. Measurements of all necessary operating parameters for analysed sealing steam condenser were performed during the ship exploitation and they were used for calculating the energy and exergy efficiency of this device. Except the displayed movement of both efficiencies the reasons for those changes and proposals for possible improvements were presented. Also, it was displayed all operating parameters of sealing steam condenser that has an impact on its performance and efficiency. During the ship exploitation, improvements related to the sealing steam condenser efficiency are hard to expect because improvements would cause an increase in the steam propulsion system operating costs

C.35delG/ GJB2 and del(GJB6-D13S1830) mutations in Croatians with prelingual non-syndromic hearing impairment

BACKGROUND: C.35delG/GJB2 mutation is the most frequent genetic cause of deafness in Caucasians. Another frequent mutation in some Caucasian populations is del(GJB6-D13S1830). Both GJB2 and GJB6 genes belong to the same DFNB1 locus and when the two mutations are found in combination in a hearing-impaired person, a digenic pattern of inheritance is suggested. METHODS: We examined 63 Croatian subjects (25 familial and 38 sporadic cases) with prelingual non-syndromic hearing impairment by polymerase chain reaction for the presence of the c.35delG/GJB2 and the del(GJB6-D13S1830) mutations. RESULTS: Of the 63 unrelated hearing-impaired subjects, the mutation c.35delG/GJB2 was found in 21 subjects (33.3%). In 5 of them the mutation was found in the heterozygous state, all of them being compound heterozygotes, as sequencing revealed a second mutation within the coding region of the gene in 3 subjects, and a splice site mutation in 2 subjects. The del(GJB6-D13S1830) mutation was not found in the investigated hearing-impaired Croatian subjects. CONCLUSION: Our results contribute to the knowledge of geographic distribution and population genetics of the GJB2 and GJB6 mutations in the Europeans

Exergy Analysis of Supercritical CO2 System for Marine Diesel Engine Waste Heat Recovery Application

In this research is performed an exergy analysis of supercritical CO2 system which uses various waste heat flows from marine diesel engine to produce additional mechanical power. The performed exergy analysis contains whole system as well as each system component individually. The observed system produces useful mechanical power equal to 2299.47 kW which is transferred to the main propulsion propeller shaft. Additionally produced mechanical power by using waste heat only will reduce marine diesel engine fuel consumption and exhaust gas emissions. Main cooler has the highest exergy destruction of all system components and simultaneously the lowest exergy efficiency in the observed system, equal to 32.10% only. One of the possibilities how main cooler exergy efficiency can be increased is by decreasing water mass flow rate through the main cooler and simultaneously by increasing water temperature at the main cooler outlet. Observed system has five heat exchangers which are involved in the CO2 heating process, and it is interesting that the last CO2 heater (exhaust gas waste heat exchanger) increases the CO2 temperature more than all previous four heat exchangers. Whole analyzed waste heat recovery supercritical CO2 system has exergy destruction equal to 2161.68 kW and exergy efficiency of 51.54%. In comparison to a similar CO2 system which uses waste heat from marine gas turbine, system analyzed in this paper has approximately 12% lower exergy efficiency due to much lower waste heat temperature levels (from marine diesel engine) in comparison to temperature levels which occur at the marine gas turbine exhaust

Thermodynamic Analysis of Steam Cooling Process in Marine Power Plant by Using Desuperheater

Thermodynamic (energy and exergy) analysis of steam cooling process in the marine steam propulsion plant is presented in this research. Steam cooling is performed by using Desuperheater which inject water in the superheated steam to obtain wet steam. Wet steam is used in auxiliary heaters for various heating purposes inside the marine steam propulsion system. Auxiliary heaters require wet steam due to safety reasons and for easier steam condensation after heat transfer. Analysis of steam cooling process is performed for a variety of steam system loads. Mass flow rates of cooling water and superheated steam in a properly balanced cooling process should have the same trends at different system loads - deviations from this conclusion is expected only for a notable change in any fluid temperature. Reduction in steam temperature is dependable on the superheated steam temperature (at Desuperheater inlet) because the temperature of wet steam (at Desuperheater outlet) is intended to be almost constant at all steam system loads. Energy losses of steam cooling process for all observed system loads are low and in range between 10–30 kW, while exergy losses are lower in comparison to energy losses (between 5–15 kW) for all loads except three the highest ones. At the highest system loads exergy losses strongly increase and are higher than 20 kW (up to 40 kW). The energy efficiency of a steam cooling process is very high (around 99% or higher), while exergy efficiency is slightly lower than energy efficiency (around 98% or higher) for all loads except the highest ones. At the highest steam system loads, due to a notable increase in cooling water mass flow rate and high temperature reduction, steam cooling process exergy efficiency significantly decreases, but still remains acceptably high (between 95% and 97%). Observation of both energy and exergy losses and efficiencies leads to conclusion that exergy analysis consider notable increase in mass flow rate of cooling water which thermodynamic properties (especially specific exergies) strongly differs in comparison to steam. Such element cannot be seen in the energy analysis of the same system

THERMODYNAMICAL ANALYSIS OF HIGH-PRESSURE FEED WATER HEATER IN STEAM PROPULSION SYSTEM DURING EXPLOITATION

Nowadays diesel engines prevail as ship propulsion. However, steam propulsion is still primary drive for LNG carriers. In the presented paper high-pressure feed water heater was analyzed, as one of the essential components in LNG carrier steam propulsion system. Measurements of all operating parameters (fluid streams) at the analyzed heat exchanger inlets and outlets were performed. Change of the operating parameters was measured at different steam system loads, not at full load as usual. Through these measurements was enabled the insight into the behaviour of the heat exchanger operating parameters during the whole exploitation. The numerical analysis was performed, based on the measured data. The changes in energy and exergy efficiency of the heat exchanger were analyzed. Energetic and exergetic power inputs and outputs were also calculated, which enabled an insight into the change of energetic and exergetic power losses of the heat exchanger at different steam system loads. Change in energetic and exergetic power losses and operating parameters, which have the strongest influence on the high-pressure feed water heater losses, were described. Analyzed heat exchanger was compared with similar heat exchangers in the base loaded conventional steam power plants. From the conducted analysis, it is concluded that the adjustment and control modes of these high-pressure heat exchangers are equal, regardless of whether they were mounted in the base loaded conventional steam power plants or marine steam systems, while their operating parameters and behaviour patterns differ greatly

MUTATIONS IN GENE GJB2/CONNEXIN 26 AS THE MOST FREQUENT CAUSE OF IMPAIRED HEARING

Zbog svoje učestalosti i potrebe za ranom dijagnozom, oslabljeni je sluh epidemiološki i javnozdravstveni problem. Mutacija del35G u GJB2 genu najčešći je uzrok genetski uzrokovane gluhoće, a vizualizira se PCR-metodom. Uvođenje analize mutacije u dijagnostički algoritam oslabljenog sluha omogućuje brzu, preciznu i etiološku dijagnozu, a i informativno genetičko savjetovanje. Ispitivanjem hrvatske populacije iz Istarske i Primorsko-goranske županije, mutacija je nađena u 36% osoba oslabljenog sluha, slično do sada ispitivanim populacijama ustanovljena je incidencija mutacije u populaciji novorođenčadi od 1/1091 (95CI: 1/372 – 1/3205).Due to its frequency and the implications of early detection, hearing impairment has become an important epidemiological and public health care problem. Del35G/GJB2 mutation is the most common cause of genetic deafness, visualized by the PCR method. The mutation analysis has been successfully introduced in the diagnostics of deafness, and it enables fast, precise and etiologic diagnosis, as well as informative genetic counselling. The study of the Croatian population from the counties of Istria and Primorje-Gorski kotar revealed that the del35G mutation is involved in 36% of hearing impaired subjects; the incidence of the mutation in the population of newborns being 1/1091 (95CI: 1/372 – 1/3205)