Authors : Yash Gandhi, Gaurav Khadke, Shruti Gavare, Chaitanya Gawali, Shreyas Gaware

Condensers 

INTRODUCTION 

A condenser is a heat exchanger which converts a vapor to a liquid. Actually, it turns superheated and highly-pressurized vapor into a subcooled liquid. Condensers are routinely used in steam power plants, refrigeration cycles and also in laboratory operations such as distillation, reflux, and extraction. The simplest and oldest condenser is just a long tube through which the vapors are directed, with        outside air providing the cooling. More commonly, a condenser has a separate tube or outer chamber through which water (or some other fluid) is circulated, to provide a more effective cooling. Laboratory condensers are usually made of glass whereas the condensers used in thermal power plants and refrigeration system are made of copper or aluminium. Condensers are used for efficient heat rejection in many industrial systems. Condensers can be made according to numerous designs, and come in many sizes ranging from rather small (hand-held) to very large (industrial-scale units used in plant processes).

HISTORY OF CONDENSER

 The earliest laboratory condenser, a "Gegenstromkühler" (counter-flow condenser), was invented in 1771 by the Swedish-German chemist Christian Weigel. By the mid-19th century, German chemist Justus von Liebig would provide his own improvements on the preceding designs of Weigel and Johann Friedrich August Göttling, with the device becoming known as the Liebig condenser.

                  Liebig Condenser

PRINCIPLE OF WORKING 

The condenser works based on Heat Transfer. Heat Transfer is the main principle behind the condenser working, Where Transferring of heat is done through cooling agent supplies in the chamber.

The main components of the condenser are –

Shell- Shell is the outer surface and base of the condenser. Tubes– Tubes are the main component of the condenser, Through that vapour or gas is passed. Cooling agent– To Create Temperature difference and to absorb vapour temperature, a Cooling agent is needed. Coolant inlet–  A Place, from where the coolant is entered in to shell. Coolant Outlet– A Place, Where Used coolant is passed out from the shell. Vapour Inlet– A place, where High-temperature vapour is entered into the tubes. Condensate Outlet– A place, Where condensed liquid is passed out from the tube. Non-condensing vapour outlet– A Place, Where Non-condensing vapour is passed by.

Firstly, High temperature vaporised gas is entered through vapour inlet. Now, the Coolant is throwdown in the condenser shell through the coolant inlet. When High-temperature vapour passes through tubes inside the shell, Vapour releases its heat to the coolant present in the shell through the heat transfer process. As vapour passes through tubes inside, It losses its temperature rapidly along the path. Due to a fall in temperature, Vapour starts to change its state from vapour to liquid. As falling of vapour temperature comes equivalent to the coolant temperature, Condensation is completed. Now, the vapour is fully condensed and changed to the liquid state and ready to use as feed water from the condensate outlet.

TYPES OF CONDENSERS

 

There are basically three major types of condensers used-

  1.  Air Cooled                                                         

  2.  Water Cooled

  3.  Evaporative type

 

 1. Air cooled condensers-

These types of condensers exchange heat through the air, Known as Air cooled condensers. Air-cooled types use air to remove heat from vapour or steam inside the tube. When high-temperature Steam or vapour enters the tube, Steam transfers heat to the tube and hence transfers heat into the surroundings due to the connection of air to the tube. The medium of blasting air can be natural or forced.

 

The two subtypes of air cooled condensers are-

    1A)  Natural convection

    1B)  Forced convection

       1A) Natural convection - When atmospheric air is passed through the condenser, vapour or gas inside the tube releases its heat to the surrounding atmosphere, resulting in the cooling of steam and turning to a liquid state. As the name suggests, Natural convection uses natural atmospheric air to cool the vapour and hence natural air is used as a cooling agent. In Natural convection, Fins are used to increase the overall efficiency of the condenser. Fins raised the surface area of the condenser and therefore increased Heat rejection. These types of condensers are made from Iron, Copper and Steel. These are mostly used in domestic refrigeration systems.

       1B) Forced convection- This type of condenser needs a fan or blower to circulate the air over the condenser tube to cool. As the air comes in contact with hot tubes, Air takes the hot tubes’ heat and gets them cooled. This condenser is much more efficient than natural convection because the mounted fan pressurized the natural air and passes through the condenser tubes and fins. Forced air-cooled condensers are used in domestic deep freezers, water coolers, window air conditioners. Mostly, Forced convection types are made from copper material.

Now its time to see more about water cooled condenser

   2. Water cooled condensers- Water-cooled type condensers are those, who use water as a cooling medium. These types of condensers are used in large refrigerating industrials needs. They are used in plants where loads are excessive and a large amount of refrigerant flows to the condensers. The best example of this type is- Central air conditioning plants.

There are three sub types of water cooled condensers-

  2A) Tube in tube

  2B) Shell and coiled type

  2C) Shell and tube type

    2A) Tube in tube condenser - In this type of condenser, water flows through the inner tube and while the refrigerant flows through the circular space between these two tubes. This type of condenser is also known as a Double tube condenser. In this type of condenser, Two pipes are used in pipe circumference, Where a small diameter coolant circular pipe is fitted above the bigger diameter refrigerant pipe, that’s why its name is- tube in tube or double tube condenser. The flow of refrigerant and water is arranged in opposite directions to get the maximum benefit of heat transfer. When the water enters through the inner tube in to the condenser, refrigerant exchanges its heat to the water and refrigerant gets cooled and converts vapour into the liquid state till the end of the condenser, And its obvious water becomes warmer as leave the condenser.

    2B) Shell and coil condenser - This type of condenser is made of a welded steel shell containing a coil of finned tubing. The water flows inside the coil and the refrigerant flows into the shell. When the refrigerant enters from the inlet side of the shell in hot vapour form, it contacts the coil which is the water flows inside the coil. The refrigerant & water exchange their heat where the water gets warmer and the refrigerant gets cools.

    2C) Shell and tube condenser - In this type of condenser, Shell and tube both are used, That’s why its name is shell & tube. The Straight tubes and integral fins are mounted inside the cylindrical shell. The cooled water enters from water intel mounted on the downside of the device, Then temperature vapour refrigerant enters from the top of the shell and gets de-superheated and then condensate and after that sub-cooled. The water comes from the water outlet at raised temperature due to heat exchange between the heated refrigerant and cooled water.

Now lets time for the last type of the condenser.

 3. Evaporative condenser - This type of condenser has the features of both air and water-cooled condensing facilities. Air and water are both used as a cooling medium. Water is pumped from the sump of the evaporative condenser to a spray header sprayed over the condenser coil and at the same time, the fan draws air from the bottom side of the condenser and discharges it out at the top of the condenser. The spray water comes in contact with the condenser tube surface, then it evaporates into the air streams. The source of heat for vaporizing the water is taken from the refrigerant, thereby condensing the gas. Evaporative types consume less power than water-cooled types.

After finishing up with the various types of condensers, lets discuss about the materials used in the construction and the different performance parameters.

 

 Materials in construction- Different types of materials used in construction of condensers are-

•  Copper
•  Brass
•  Steel
•  Titanium
•  Nickel

Performance Parameters of Condenser – When measuring the performance of condenser, the different points we should analyse are –

1.  Heat rejection rate
2.  temperature mass flow rate
3.  compressor power
4.  electric power input
5.  coefficient of performance

  Lets move further to the next parts which are Advantages, Disadvantages and applications of condenser.

 Advantages of Condenser-

·       It increases the expansion ratio of steam, and hence increases the efficiency of the plant.

·       It reduces the backpressure of the steam, and thus more work can be obtained.

·       It reduces the temperature of the exhaust steam, and its increasing work efficiency.

·       The reuse of condensate as feed water for the boilers reduces the cost of power generation.

·       The temperature of the condensate is higher than that of the freshwater, therefore the amount of heat supplied per kg of steam is reduced.

·       Useful in Obtaining the better vacuum

·       Less space is required 

Disadvantages of condenser –

·       Installation cost is more.

·       It required more maintenance.

·       Operating the water-cooled condenser is not easy.

·       It is not so flexible to use everywhere.

·       It required an additional recirculation system for used water.

·       Water cooled condenser parts undergo to corrosion effect.

Applications of condenser –

•  Automotive - condensers designed for use in automotive or vehicular air   conditioning systems (e.g. cars, planes, trains).
•  Building - condensers used to provide central air conditioning for buildings. They   can be mounted outdoors, either on the ground or rooftop.
•  Process - condensers used in cooling units for in-process fluids.
•  Refrigeration - condensers used in refrigeration systems.
•  Steam power turbine - Surface condensers used in power generation facilities   such as nuclear power plants to condense turbine exhaust steam into water.

Efficiency of condenser –

 The efficiency is calculated by formula