Cooling Design Analysis of The Use of Land Engine On Ship

Based on the survey, the majority of fishermen in Indonesia choose to use land engines as propulsion for the main engine and auxiliary engine on ships because in terms of the price of land engines, they are much cheaper than ship engines produced by marine engine factories. Therefore, not a few workshops that often serve land engine modifications for further use as ship propulsion. Regulations regarding the use of land engines as ship’s main engines in Indonesia are currently not widely regulated in the Classification Agency regulations. Heat exchanger that supports the cooling system for optimal use of land engines on ships. Furthermore, the heat exchanger design process with a heat transfer load of 17,416 Watt was carried out using the LMTD method and obtained a heat transfer area value of 1,204 m2 with a staggered arrangement configuration. From the results of the CFD simulation, the temperature value at the hot water outlet is 51.39 C.


Introduction
The prime mover on traditional fishing boats on generally use land machines (Land use), the use of land machines preferred because it has many advantages for fishermen, namely the price is much cheaper than marine engines [1].For information that for regulations on the use of land machines in thnm e ship has not been specifically regulated in the Classification board.Based on BKI part 1 vol 3. Machinery installations which have been developed on novel principles and/or which have not yet been sufficiently tested in shipboard service require the BKI's special approval.Such machinery may be marked by the Notation "EXP" affixed to the Character of Classification and be subjected to intensified survey [2].
A significant difference from land engines and ship engines is in the cooling system of the engine, in general land engines use a radiator type cooling system using air to cool the engine coolant, while ship engines often use a heat exchanger type cooling system, which uses seawater to cool the engine coolant.According to data from KNKT, the majority of fish boat accidents are caused by engine damage (57%), sinking (18%), ship collision (5%) and others.Engine damage is caused by several fators such as cooling system failures, lubrication system failures and others, cooling system failures are caused by the lack of ability of the heat exchanger to cool the cooling water in the engine so that the engine will overheat and damage occurs.Modification of the cooling system is needed to overcome the problems that may arise.Therefore, the purpose of this research is to design a cooling system for the use of land engines on ships.This cooling system design is expected to be able to cool the engine optimally and is intended to be a basic reference in modifying the land engine cooling system for use on ships, especially to support shipping safety aspects and regulation regarding to Indonesian Classification Bureau.
The reason for this research is to reduce the potential for damage due to failure of the cooling system on the ship, both to the engine.Modification of the cooling system is needed to overcome the problems that arise, one method of solving it is by re designing and calculating the cooling system requirements.The purpose of this modification is to determine the value of heat transfer requirements in the cooling system which will later become a reference for standardization in modifying the land engine cooling system for further use on ships.

Methods
To define the design of cooling system we must calculate the heat transfer rate requirement using LMTD method that calculating the difference temperature between inlet temperature and outlet temperature of the heat exchanger, the value of temperature can be defined by looking from the manual book from the engine.And then the LMTD value got correction by correction factor based on the temperature design.

Figure 1. Table of Corection Factor
At the first step we design the heat exchanger, we choose engine Maker: ISUZU Model : BB-6BG1TRB-05 (6 cylinder) Type : 4 stroke in-line, turbocharge Rated Power : 143 HP @1800 RPM with considerations of choosing this engine is Availability of spare part Ease of CARE WORKSHOP.According to BKI guideline regulated power of land engine which applied as ship propulsion at 75% of the BHP.To finding the U 1 we must analysis every coefficient convection from the each fluid (sea water and fresh water) and coefficient conduction of tube wall.To find the coefficient convection of freshwater we must define the Reynold Number through tube bank.And we can find the Nusselt number for finding the coefficient convection of fresh water.For the sea water, step to define coefficient convection is almost same as fresh water, but the difference is the Reynold number through inside tube, to find mean viscosity each tube we can divide the sea water mass flow rate with total of tube and then from the Reynold number can define Nusselt number and coefficient convection of sea water, After coefficient convection of sea water and fresh water defined, we calculate total of heat transfer coefficient (U 1 ).After we find the U 1 we can calculate the actual heat transfer area use U 1 and define number of tubes.With designed number of tube and arranged with staggered arrangement we can find the shell inner diameter.And after they dimension of the heat exchanger defined we must validating the calculation of the number of tube with the Reynold number through inside the tube.And after that we can calculate the pressure loss and the head loss of heat exchanger and the piping system, the value of head loss is to calculate the power of sea water pump.Because the sea water pump is driven by belt and take power from the engine so we need to define the power loss due to pump load at the engine power.And the do the validating power due to power requirement on the shaft.

Engine Choosing
Data analysis was carried out on fishing training vessels 15 GT.Designed as a fishing vessel that can be used for operating fishing gear.The selection of land engine as the main propulsion according to the design engine power requirement on the MCR condition.But according to BKI guideline for the use of land engine as main propulsion regulated to 75% of the BHP.So that it can determine the selection of machines and the specifications of the land use type machines that are required from this 4 analyzed vessel.As for the selected machine to be used as a ship propulsion based on the considerations of reference power rate, availability of machines in the market, ease of maintenance and availability of spare parts The following are the main data of this machine: Maker : ISUZU Model : BB-6BG1TRB-05 (6 cylinder) Type : 4 stroke in-line, turbocharge Rated Power : 143 HP @1800 RPM Idle speed : 900 RPM Coolant capacity : 8.5 l

Heat transfer calculation
Determining the cooling system of heat exchangers and seawater pumps is the main thing to determine the temperature of the water coming out and the temperature of the inlet water from the engine and the temperature of the sea water around the waters [3][4].Based on the data from the BG series manual book, the output temperature of the engine must be between 80-85 and taken at 85℃, while the entry temperature for the engine is between 50-55℃ and taken at 55℃.Meanwhile, sea water temperature data from the research center.Indonesian marine waters are between 25-30℃ and taken 30℃.So Tout,engine;Th,in = 85℃, Tin,engine;Th,out=55℃, Tin,seawater ; Tc,in = 30 ℃.So the total heat transfer rate can be as follows:

LMTD
The LMTD method is a heat exchanger analysis [6][7] method by calculating the average temperature between the hot flow liquid and cold flow liquid.Because the flow that work in shell and tube is counterflow so the LMTD equation is known as follow:

𝑇
To determine the value of ∆t, a correction factor (F) value is needed from the figure below

Determine heat transfer surface area
After the LMTD value is defined [8], the next step is to determine the energy transfer surface area, the heat transfer area can be found using following equation: In this case the heat transfer coefficient can be seen in table 1 as the initial U or Ud, which will later be used to determine the actual U value acting on the heat exchanger.
From this range it is taken at 850 W/m2K, so the equation is as follows:

Determine number of tube
After the heat transfer area is known, the next step is to determine the length of the tube, the number of tubes, the diameter and the determination of the tube material.Tube is a small pipe that is arranged in a shell, in the design of the tube the arrangement of the tube on the tube sheet is divided into four types as shown in Figure 4.The tube is arranged in a triangular pitch configuration which has the highest coefficient.

Figure 4. Tube Arrangement
In this case the length of the tube is assumed to be L = 0.5 m taking into account the space needed in the engine room, the diameter and tube material used is 3/8 inch stainless steel which has an inner diameter profile (id) = 0.014 ,. outside (od) = 0.0173 m. the number of tubes can be determined by the following equation:

𝑐
Based on TEMA 9 th edition the distance between the tubes from the center point [5] is determined by a range of 1.25-1.5 multiplied by the outer diameter I (od), so that the tube pitch (pt) = 1.5x0.0173m= 0.026 m. while for the size of other parts described as Figure 5

Coefficient convection of fresh water
The next step is to find the convection coefficient of each part of the heat exhenger element such as the convection coefficient of fresh water and sea water [9], to determine the value of the convection coefficient in fresh water, first determine the Reynold number, because fresh water passes through the tube arrangement, the Reynold number trough tube bank formula as follows: For a staggered arrangement, the fluid approaches through area A1 in Figure 4.3, passes through area At and then through area 2 Ad while enveloping the next pipe, if 2Ad > At, the maximum velocity still occurs between the tubes and the maximum velocity is defined to be: The value of the kinematic viscosity of the fluid can be seen from the water properties table, so the Reynolds number can be determined as follows: The following is the correlation from table 2 for the number of tubes more than 16 (Nt>16), 0.7 < Pr < 500 and 0 < ReD < 2 x 106.

Table 2. Range and correlation value
Based on table, the equation becomes: From the value of the Nusselt number [11], it can be seen that the convection coefficient value of hot water flowing outside the tube, the value of the thermal conductivity of water obtained from the water properties table is, k = 0.6475 W/mK, then the value of the fresh water convection coefficient is defined as follows.8

Determine coefficient convection of sea water
The mass flow rate of seawater that has been defined previously is the total flow rate of all tubes, while for each tube it can be assumed as the mass flow rate divided by the number of tubes (ṁ/Nt), while the kinematic viscosity can be seen from the water properties, so the equation above is changed to: The flow is said to be fully developed hydrodynamically if the velocity profile no longer changes the direction of the flow.In laminar flow of highly viscous liquids, the velocity profile forms a poiseuillean parabola just after the inlet.In this case the identified fluid has fulfilled the fully developed requirements.As an approximate solution for developed laminar flow, the equation is as follows: Then a correction is made for the value of Nu from the value of Nu0 in this case applies to the range 0.1≤ Pr , so that the results of Nu are as follows: The value of the thermal conductivity of seawater is k = 0.6161 W/mK, so the value of the heat convection coefficient in cold water (sea water) can be seen as follows:

Determine Thermal Resistance
After all the convection coefficients for each element are met, the total thermal resistance value (U1) can be found where the thermal conductivity value of stainless steel is k = 15 W/mK and the fouling factor value for hot water is Rfh = 0.0002 m2K/W and the value of the water fouling factor.cold Rfc = 0.0001m2K/W.Then the equation U1 is described as follows: The value of thermal resistance U1 is used as a reference to determine the actual number of tubes, then to determine the number of tubes as follows:

𝑄
The number of tubes is adjusted to the arrangement and the number of standards on the tube stack is 55 pieces.The shell diameter is adjusted to the number of tubes and the pitch distance so that it is obtained from the calculation results of 111 mm, but the shell diameter is adjusted to the availability of materials, in this case the shell design uses a steel pipe, following the availability of materials, with 5

Validating heat exchanger design
The need for validation after determining the number of tubes aims to determine whether the energy exchange acting on each part can be fulfilled.Calculation details as follows: With a value of X = 0.0256, the equation for the nusselt number becomes: So that the actual value of U can be known as follows: And to find out the actual heat energy transfer surface area and number of tube as follows: The number of tubes is still below the standard number that has been designed previously, which is 55, so for this design it can be accepted and simulations are carried out in the next step.

Pump Determination
After the design and simulation of the heat exchanger is done.The next step is to choose a pump to supply seawater from the sea chest to cool the components, cool the fresh water that cools the engine and then exit through the overboard.Pump selection is determined based on the total head, the total head is planned by considering the location in the engine room and the pressure drop on the heat exchanger.The value of the pressure drop in the heat exchanger is as follows: The average fluid velocity Vavg = 0.037 m/s, while f is the Darcy-Weisbach friction factor, f = 0.124.After the pressure loss value is obtained, the head loss value is obtained by the following equation.
The total head loss is determined from the pipe design designed in the engine room, the total static head in the seawater piping system is hs = 0.7 m and the friction loss in the pipe hf = 0.3 m.The total head loss of seawater pipes can be described as follows: And then we choosing pump for sea water From the pump specifications, the maximum pump discharge is 72 l/min = 0.0012 m3/s and the pump speed can be adjusted to the engine speed so that it can be coupled to the crankshaft pulley as shown in figure 7. The designed of cooling system using heat exchanger shell and tube is heavier than the previous design using radiator and the working temperature can be maintained around 52.3℃ while using heat exchanger.

Figure 8. Pump Instalation Guidance
This is the comparison in equipment weight when using air cooled and when using a heat exchanger.Equipment weight before the modification are 19 kg, with radiator on empty condition.And weight after modification are 21 kg, Heat Exchanger measured on the Ansys Software, so maybe the real weight got more or less than 13,1 kg.Also, a comparison of the working temperature of the machine when using air cooled and when using a heat exchanger.All water temperature measurement done by looking at Ansys Software and ignoring outside environmental influences.Based on the Manual book of the engine, temperature of cooling water at engine water jacket inlet shouldn't more than 65 ℃.When the cooling system change into shell and tube, the temperature of cooling water at engine water jacket inlet reach 52,3 ℃, that mean the system can cooled the coolant better than the previous design.

CONCLUSIONS
To design the dimensions of the heat exchanger it takes the value of the average temperature difference of the heat exchanger system of 29.72 ℃.From the difference temperature, it can be seen that the effective heat transfer surface area is 1.2 m2, with a planned tube length of 0.5 m and a tube diameter of 10 mm, the value of the number of tubes is 55 pieces.The tubes are designed in staggered arrangement with a triangular pitch, so that the shell diameter is 0,121 m with a thickness of 5 mm. the system get 3 kg more heavy than previous design.And then after running the system by simulation on Software the cooling water temperature reach 52,3℃ before engine water jacket inlet.

Figure 5 .
Figure 5. Staggered Arrangement pipe, it is determined the inner diameter of the shell ID = 126.6 mm, and the outer diameter of the shell OD = 139.8mm with the thickness t = 6.6 mm.In accordance with TEMA Shell [11] is designed with configuration B, E, M where this code refers to the design of the head and body heat exchanger.For notation B and M, it is a fixed head type that has a lid that cannot be opened, while for notation E it is for a body model with one pass shell.

Figure 6 .
Figure 6.Shell Design the conductivity value of seawater become:

Figure 7 .
Figure 7. Pump Model and Specs

Table 1 .
Second step is to calculate the heat transfer.at this system water from engine jacket controlled by thermostat.If water goes 85 C thermostat will fully open and fresh water flow to heat exchanger.But if water not reach 85 C thermostat closed and flow to expansion tank, With inlet to heat exchanger 85C ang outlet 55C and sea water inlet 30 and temperature at outlet assume as 50C that can calculate the heat transfer rate.From the heat transfer equation we can define the design of tube and shell with LMTD method.LMTD is logarithm difference temperature between inlet and outlet in the heat exchanger.the difference got correction by correction factor that can see as the figure of correction factor.From the LMTD value got define Heat transfer Area can be define too.At the first trial we assume the U d (coefficient of heat transfer) from the table.This is used for designing initial design and to finding the U 1 .Representative values of the overall heat transfer coefficients in heat exchangers