A coiled source is a device for supplying and storing sanitary hot water, and the most common method for producing sanitary and consumer hot water and storing, it is to use coiled sources.
The heat exchange made heats the copper pipes thus as a result heats the cold water around the pipes that is inside the tank.
This device is placed subset of heat exchangers and pressure vessels.
These tanks are designed and manufactured in different dimensions and sizes with different thermal capacities according to the customer's request.
Division of coil sources:
1. In terms of heat exchange fluids:
a) water-water b) steam-water
This division is related to the boiler in the engine room, it determines the type of fluids.
2. In terms of the structure of the storage tank
a) Horizontal pressure vessels b) Vertical pressure vessels
a:
In this type of fluid coil sources, the carrier and receiver of energy are both in the liquid phase of water. The use of these types of converters is common.
The hot water produced in these sources is mostly used for sanitary purposes.
b:
In this type of coil sources, the heating fluid is steam, which is supplied from the boiler. The produced hot water can be used for heating or for service or similar things.
This classification is related to the tank of the machine, and factors such as the dimensions of the engine room can be involved in the selection of the parameters of this classification.
Calculations:
Coil tank(steam-water):
Q=8.33×V ̇×∆T Q: Amount of heat required (Btu/hr)
m ̇=Q/hfg V: Consumption hot water discharg (gph)
∆T: The temperature difference between hot
water outlet and cold water inlet (F)
m: Required steam flow rate (lbs/hr)
hfg: Latent heat of vaporization at the desired
pressure (Btu/Lb)
The coils used in the mentioned sources are usually made of copper and U shaped. This coil is designed and manufactured at different thermal levels according to the customer's needs.
The required parameters that the customer must provide to the manufacturer to order the coil source:
Flow of hot water consumption
Heat capacity
The thermal surface of the coil and its volume
Required hot water temperature
Tank dimensions
Type of heating fluid
How to control hot water temperature?
Controlling the temperature of the hotwater is done by two common methods, which are generally mentioned below.
1. Changing the pump speed and turning on and off the hotwater circulation pump between the boiler and the coil source:
In this method, when the temperature of the water inside the tank reaches the set limit, the thermostat installed on the body of the power source gives the command to change the speed or turn off the pump and the circulating water flow is reduced or interrupted, and when the water temperature inside the tank exceeds the set limit If the temperature sensor is lower, it gives the command to increase the speed or turn on the pump.
2. Use of motorized three-way valve:
Another way to control the temperature of the hotwater inside the tank is to use a mixer-type motorized valve that is interlocked with a thermostat installed on the coil source. The description of this method is that when the temperature of the water inside the tank rises, the motorized valve gradually closes the return path of the heating water and opens the bypass path to the same extent, so that the heating water does not enter the coil and as a result, no heat exchange. With the heated water in the tank, it returns directly to the boiler. This prevents the temperature of the water inside the tank from increasing beyond the permissible limit.
Dos and don'ts of coil sources:
The body of the coil source should be made of steel or galvanized, and its inner and outer coating should be water-resistant with epoxy paint.
The tank should have an inspection gate with dimensions of at least 300~400 mm.
The diameter of the copper pipes used in the coils is usually 3/4 or 7/8 in.
The maximum working pressure of coil sources should not exceed 10 bar.
Installation & setting up
1. Provide enough space for insulation around the tank and pipes
2. Source connections up to two inches in diameter should be ribbed and above two inches should be flange.
3. The coil source must be installed on a suitable foundation (concrete and at least 10 cm).
4. A suitable space should be provided around the source for servicing and replacing its coil.
5. To reduce energy losses, the body of the tank should be insulated with a suitable insulation with a diameter of at least 40 mm
6. For suitable insulation, insulators with polymer base which has aluminum foil and one adhesive side so than it can be installed on the tank more easily.
7. The source should have a proper safety valve and its outlet pipe should extend up to 300 mm from the floor without any obstacles.
8. The source should have a suitable thermometer with a suitable temperature range for the device.
9. The flow of cold water inside the tank leaves illuviation, so it is better to use magnetic or electronic hardeners on the way of cold water entering the tank.
Reversible hot water route & Its circulator pump
In systems where the length of the sanitary hot water path from the coil source to the last consumer is so long that if hot water is not consumed after a limited period of time, the water in the pipes gets cold. When using hot water, first the water in the pipes that has lost its heat, is removed from the consumer and then the freshly removed water is deprature from the source. This wastes a lot of water. To solve this problem, should use a route, the hot water reversible pipe, to prevent the water from flowing through the hot water reversible pipe in the distance between the consumer and the coiled source, from reducing the temperature of the water inside the pipes too much.
In cases where the tube is too long a circulator pump should be used to circulate the water inside the pipes. In order to control the circulator pump, we interlock the thermostat on the return pipe with the pump so that if the water temperature in the pipes decreases, the pump will circulate the water in the system.
In order to control the circulator pump, we interlock the thermostat on the reversal pipe with the pump so that if the water temperature in the pipes decreases, the pump will circulate the water in the system.
Calculation of flow rate and reversible hot water circulator pump head:
V ̇=((LS×q))/(500×∆T)
Hp = [(LS+ LR )×1.5]×[Rate of pressure drop in pipe]
LS : Path length of
LR :
Q: Heat transfer rate per unit area of the pipe
∆T:
V:
Hp : Pump head
Rate of pressure drop in pipe:
The rate of pressure drop that we usually consider is 2.5%
Safety recommendations:
first safety then work
During installation, start-up and repairs, use safety equipment including glasses, shoes and gloves.
Installation must be done according to the manufacturer's instructions.
The work related to the electrical panel of the devices and electrical connections of the electromotor and controls should be done by trained people who are aware of the principles of industrial electricity.
Be careful of burns caused by the release of hot fluid when servicing the boiler and pressure sources with hot fluid and when testing the safety valve.
Check the piping and fittings to make sure they are installed correctly.
Ensure proper installation of controls and valves and proper orientation.
Make sure the safety valve is working properly.
During installation, pay attention to all the warnings of the company representative.