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How do you calculate the flow rate of a heat exchanger?

How do you calculate the flow rate of a heat exchanger?


  1. The main basic Heat Exchanger equation is: Q = U x A x ΔTm =
  2. The log mean temperature difference ΔTm is: ΔTm =
  3. (T1 – t2) – (T2 – t1) = °F.
  4. T1 = Inlet tube side fluid temperature; t2 = Outlet shell side fluid temperature;
  5. ln (T1 – t2) (T2 – t1)

How do you calculate heat transfer area of a plate heat exchanger?

Calculation method

  1. Heat load, Theta and LMTD calculation. Where: P = heat load (btu/h) m = mass flow rate (lb/h)
  2. Heat transfer coefficient and design margin. The total overall heat transfer coefficient k is defined as: α1 = The heat transfer coefficient between the warm medium and the heat transfer surface (btu/ft2 h °F)

How is the logarithmic mean temperature difference calculated for heat exchangers?

by definition given above, LMTD for counter current flow = (60-50) / ln(60/50) = 10 / 0.1823 = 54.850C. For co-current heat exchanger, ΔT1 = TH1 – TC1 = 100 – 30 = 700C (At first end hot and cold fluids enter the heat exchanger.) (At the other end hot and cold fluids exit the heat exchanger.)

What is lmtd formula?

Log Mean Temperature Difference (LMTD) is an indicator of the average temperature difference between the hot and cold fluids in a heat exchanger. It is calculated using the following equation – ΔT1 → the temperature difference between hot and cold fluids at one end of the heat exchanger.

What is unit of lmtd?

The log mean temperature difference (LMTD) is used to determine the temperature driving force for heat transfer in flow systems, most notably in heat exchangers. The LMTD is a logarithmic average of the temperature difference between the hot and cold streams at each end of the exchanger.

What is NTU in heat exchanger?

The Number of Transfer Units (NTU) Method is used to calculate the rate of heat transfer in heat exchangers (especially counter current exchangers) when there is insufficient information to calculate the Log-Mean Temperature Difference (LMTD).

What is HTU and NTU?

The number of transfer units (NTU) required is a measure of the difficulty of the separation. The height of a transfer unit (HTU) is a measure of the separation effectiveness of the particular packings for a particular separation process.

What is capacity ratio of a heat exchanger?

Capacity ratio (C): It is defined as ratio of minimum to maximum capacity rate of fluids being used in a heat exchanger. as cmin = mh cph and cmax = mc cpc. The fluid with lower heat capacity rate will undergo greater change in temperature as compared to fluid with higher heat capacity rate.

Which of the following is not an example of recuperator type heat exchanger?

6. Which of the following is not an example of recuperators type heat exchanger? Explanation: Recuperators are not used in chemical factories.

What are the examples of heat exchanger?

The classic example of a heat exchanger is found in an internal combustion engine in which a circulating fluid known as engine coolant flows through radiator coils and air flows past the coils, which cools the coolant and heats the incoming air.

Which of the following is a type of heat exchanger?

Some of the types of shell and tube heat exchangers available include helical coil heat exchangers and double pipe heat exchangers, and some of the applications include preheating, oil cooling, and steam generation. A close-up view of a heat exchanger tube bundle.

Which is not associated with heat exchanger?

Which of the following is not associated with a heat exchanger? Explanation: The correction factor i.e. Mc Adam’s is associated with laminar film condensation on a vertical plate. Explanation: Effectiveness = (t h 1 – t h 2) C h /C MIN (t h 1 – t c 2). Explanation: NTU = U A/C MIN = 5.2.

Which of the following is NOT a plate type heat exchanger?

Which of the following is not a Plate – Type heat exchanger? Explanation: Plate type heat exchangers can be classified as Gasketed, brazed and Welded (full or semi). Other categories are plate coils, spiral plate, etc.

What is the general range of NTU in heat exchanger design?

NTU is defined as:[11.74]NTU=UACminwhere U is the overall heat transfer coefficient (kW/m2K), A is the heat transfer area of the heat exchanger (m2) and Cmin is the smallest thermal capacity of the two fluids (kW/K).

What is meant by effectiveness in heat exchanger?

Effectiveness of a heat exchanger. The effectiveness (ϵ) of a heat exchanger is defined as the ratio of the actual heat transfer to the maximum possible heat transfer.

Which heat exchanger is most efficient?

Plate exchanger is the most efficient due to turbulent flow on both sides. High heat-transfer coefficient and high turbulence due to even flow distribution are important. However, a plate heat exchanger regenerator is restricted to low viscosities. With high viscosities, a special tubular may be required.

What is parallel flow heat exchanger?

In heat exchanger. This flow arrangement is called parallel flow. Heat is transferred from the warm fluid through the wall of the inner tube (the so-called heating surface) to the cold fluid. A heat exchanger can also be operated in counterflow, in which the two fluids flow in parallel but opposite directions.

How can you increase the effectiveness of a heat exchanger?

Here are 5 proven industry practices to boost heat exchanger performance and maintain process efficiency:

  1. Online and Offline Cleaning.
  2. Maintaining Heat Exchanger.
  3. Periodic Cleaning.
  4. Cleaning the PHE Manually.
  5. Minimizing the Fouling Factor.
  6. Analyzing and Addressing Issues in Heat Exchanger Efficiency.

How do you increase heat transfer area?

The convection coefficient may also be increased by an insert of a twisted tape that consists in a periodical twist through 360 degrees. Tangential inserts optimize the velocity of the flow near the tube wall, while providing a bigger heat transfer area.

How do you design a heat exchanger?

For the sizing problem:

  1. Calculate the effectiveness.
  2. Calculate the capacity rate ratio.
  3. Calculate the overall heat transfer coefficient.
  4. Determine NTU.
  5. Calculate the heat transfer surface area.
  6. Calculate the length of the tube or heat exchanger.

What are the factors that can affect the efficiency of a heat exchanger?

The main factors affecting the performance heat exchanger tubes include: fluid velocity, tube diameter, converter tube shape (U or cross shape), converter layout order (horizontal or vertical), and Venting valve, material of tube sheet and channel and location order of input channel.

What are the three factors affecting heat transfer?

Factors that affect rate of heat flow include the conductivity of the material, temperature difference across the material, thickness of the material, and area of the material. Different materials have greater or lesser resistance to heat transfer, making them better insulators or better conductors.

How does heat flow in a system?

Heat moves in three ways: Radiation, conduction, and convection. Radiation happens when heat moves as energy waves, called infrared waves, directly from its source to something else. This is how the heat from the Sun gets to Earth. In fact, all hot things radiate heat to cooler things.

What are the factors affecting heat?

Environmental factors

  • Air temperature. This is the temperature of the air surrounding the body.
  • Radiant temperature. Thermal radiation is the heat that radiates from a warm object.
  • Air velocity.
  • Humidity.
  • Clothing insulation.
  • Work rate/metabolic heat.

What are the two factors that affect heat energy?

The two important factors that affect heat energy are specific heat and temperature. Specific heat is a heat-constant of a material per unit mass per degree of temperature change (in units of energy per mass and temperature), like Joules/Kg-°C .

What are the four comfort factors?

Let’s look at all four factors of comfort now:

  • Temperature. How hot or cold is it? Humans like to be in the range of 70 to 80 degrees, more or less.
  • Humidity. How much moisture is in the air? Forty to sixty percent relative humidity is the ideal range.

What factors affect heat transfer between a warm and a cool substance?

The amount of time of contact, the area of contact, and the specific heals of the substances, the factors affect heat transfer between a warm and a cool substance. Explanation: Heat transfers from a very hot body always, and into a colder body.

What happens when two objects with different temperatures are in contact?

If two objects at different temperatures are brought in contact with each other, energy is transferred from the hotter object (that is, the object with the greater temperature) to the colder (lower temperature) object, until both objects are at the same temperature.

What is used to measure heat?

Two classes of instruments are employed for the measurement of heat, namely, thermometers and pyrometers. Thermometers are only employed to measure comparatively low temperatures, and we shall confine our remarks entirely to this class in the present article.

At what point will the heat flow stop?

When will heat flow between the objects stop? Heat will always flow from the warmer object to the colder object. The heat transfer will stop when the two objects are at the same temperature and reach thermal equilibrium.