How do you calculate heat exchanger velocity?
V = Velocity (ft/sec), the calculation is:
- Example: A heat exchange with a flow rate (F) of 100 gpm through a heat exchanger with 2 passes (P) that has 100 tubes (N) with diameters (D) of 1 inch will have a velocity of 0.82 ft/sec:
- Is that good?
- Using the relationship ν = µ / ρ, we can simplify:
What is the difference between velocity and flow rate?
Flow is a measure of air output in terms of volume per unit of time. The common units are litres per minute, cubic feet per minute (CFM), etc. Velocity refers to how fast the air is moving in distance per unit of time. The common units are feet per second, metres per second, etc.
How does velocity affect heat transfer?
The fluid motion enhances heat transfer (the higher the velocity the higher the heat transfer rate).
How do you calculate the flow rate of a heat exchanger?
Using the equations, UA/(mccpc) = (Tc2- Tc1)/LMTD and UA/(mhcph) = (Th1- Th2)/LMTD , where A is surface area, 3.1417 do L , mc mh, cpc, cph are mass flow rates and specific heats of cold and hot fluids 9determined by temperatures of fluid at bulk temperatures from data book, mass flow rates can be determined.
How is flow velocity measured?
A pitot tube is used to measure fluid flow velocity. The tube is pointed into the flow and the difference between the stagnation pressure at the tip of the probe and the static pressure at its side is measured, yielding the dynamic pressure from which the fluid velocity is calculated using Bernoulli’s equation.
How does flow rate affect heat exchanger performance?
In other words, the rate of heat transfer is directly proportional to mass flow rate. If you increase the flow rate, you will then increase the rate of heat transfer. Since you cannot mess with mother nature, it is very naive to think it works any other way.
What is heat exchanger efficiency?
The heat exchanger efficiency is defined as the ratio of the heat transferred in the actual heat exchanger to the heat that would be transferred in the ideal heat exchanger. The concept of heat exchanger efficiency provides a new way for the design and analysis of heat exchangers and heat exchanger networks.
Is flow and flow rate the same?
Yes they are the same thing. Volume flow rate is the same as “Flux” and “R”. There are two different equations used to express volume flow rate, it can be expressed as Volume/Time. Another equation to express volume flow rate is, Cross sectional Area(Distance/Time) or Cross sectional Area(Velocity).
How does flow rate affect heat transfer in heat exchanger?
The heat transfer always increases with the increase in flow rate.
How do you find velocity from flow rate and pressure?
In order to determine the Flow Rate represented as Q, we must define both the volume V and the point in time it is flowing past represented by t, or Q = V/t. Additionally Flow rate and velocity are related by the equation Q = Av where A is the cross-sectional area of flow and v is its average velocity.
What are two ways to measure flow velocity?
Common Flow Metering Methods in Open Channels
- Eyeball Method.
- Depth to Flow (Manning’s)
- Primary Device.
- Area-Velocity Meter.
- Transit Time Meter.
- Venturi Meter.
- Turbine Flow Meters.
- Magnetic Flow Meter.
Does increasing flow rate increase heat transfer?
How does flow rate affect temperature?
Mass flow rate and temperature equation As we have discussed above, the temperature difference in the system is inversely proportional to the mass flow rate in the system. That is, as mass flow rate increases the temperature difference decreases.
What is the maximum velocity of a heat exchanger?
The actual maximum velocity for this application varies with heat exchanger diameter and nozzle opening sizes. Some copper tube selections may have maximum velocities as high as 7.5 feet per second (FPS) while others have a maximum as low as 6.5 FPS. Stainless steel and Cupro-Nickle (CuNi) velocities may go as high as 11 FPS.
What is a counterflow heat exchanger?
A counterflow heat exchanger has the hot fluid entering at one end of the heat exchanger flow path and the. cold fluid entering at the other end of the flow path. Counter flow is the most common type of liquid-liquid heat exchanger, because it is the most efficient.
How does a cross flow heat exchanger work?
In a cross-flow heat exchanger, the fluids travel roughly perpendicular to one another through the exchanger. For efficiency, heat exchangers are designed to maximize the surface area of the wall between the two fluids, while minimizing resistance to fluid flow through the exchanger.
What is the minimum flow rate of water in a heat exchanger?
Minimum Water Velocity in Shell and Tube Heat Exchangers. In most heating applications, the flow rate has to drop down to below 5% of the design before there is an issue. In most heating applications with water above 50°F, there are other devices such as pumps that have higher minimum flow requirements than the heat exchanger.