The steam transfers heat to a fluid at the tube side . The steam condenses during this process and leaves the shell side at the port B at a temperature Ts. The tube side fluid enters the heat exchanger at C with a flow rate of M kg/s at a temperature Ti and leaves at D at a temperature To. The heat loss QH from the steam can be expressed as QH = W(? + CpH. (Tv-Ts)) Similarly, the heat gained by the tube side fluid QC can be expressed as QC= M. CpT. (Ti-To) The heat transfer coefficient for the shell side and tube side hH and hc can be estimated using QH = hH .? TM and QC = hC.? TM . Page 1 of 15 Experiment 8 – Free & Forced Convection
Convection Heat Transfer. doc STEAM AT TV ENTER AT PORT A TUBE SIDE FLUID ENTERS AT Ti TUBE SIDE FLUID LEAVES AT To CONDENSED STEAM LEAVES PORT B AT TEMPERATURE TS FIGURE 8. 1 BASIC LAY-OUT OF A SHELL AND TUBE HEAT EXCHANGER Calculation of the individual heat transfer coefficients involves the following dimensionless numbers: The Nusselt number, Nu . where ? = individual heat transfer coefficient [W/m2·K] d = characteristic length [m] (e. g. tube diameter) ? = thermal conductivity [W/m·K] cp = specific heat J/kg·K] ? = dynamic viscosity [Pas] v = velocity [m/s] ? = density [kg/m3] The Prandtl number, Pr The Reynolds number, Re Page 2 of 15 Experiment 8 – Free & Forced Convection Convection Heat Transfer. doc For natural convection one dimensionless number is added: The Grashof number, Gr where g ? ?T = gravitational acceleration [m/s2] = volumetric expansion coefficient [K-1] = temperature difference [K] . At natural convection the following generalized equation applies: . At forced convection the following generalized equation applies: With dimensionless numbers and equations any consistent system of units can be applied. .
The Term Paper on Impact Of Mixed Convection On Ceiling Radiant Cooling Panel Capacity
The main thrust of the research described in this paper was to develop a simplified method of accurately estimating the impact of mixed convection on the cooling capacity of a ceiling radiant panel in mechanically ventilated spaces. The simplified correlation for mixed convection heat transfer was derived from established mixed and natural convection correlations. It was found that the total ...
The physical meaning of the different dimensionless numbers is as follows: Nu = (characteristic length)/(theoretical film thickness) Pr = (momentum diffusivity)/(thermal diffusivity) Re = (momentum by eddy diffusion)/(momentum by molecular transport) Gr = (inertia forces)/(viscous shear forces)·(buoyancy forces)/ (viscous shear forces) The following equation is valid for laminar flow conditions (Sieder & Tate): . where ? dh A s ? ?b ? L Re Pr = individual heat transfer coefficient [W/m2·K] = hydraulic diameter [m] = 4·A/s = cross-sectional area [m2] = wetted perimeter [m] = thermal conductivity [W/m·K] = dynamic bulk viscosity [Pas] = dynamic wall viscosity [Pas] = tube length [m] = Reynolds number = Prandtl number The equation is valid for: Page 3 of 15 Experiment 8 – Free & Forced Convection Convection Heat Transfer. doc A large number of other equations are also available in literature, for different fluids, flow conditions and geometries 8. 3 APPARATUS The layout of the equipment is shown in Figure 8. The apparatus consists of a constant head glass feeder tank E (6”OD x 5 5/8” height) fitted with a vented aluminium top and bottom plate. The bottom plate is connected to a water inlet E1to the tank and also to a water overflow outlet E2 through a weir. A weir overflow drain pipe E3 is adjustable vertically through weir adjustment grip ring W, a packing gland assembly located near the middle of the line. Once the weir height is adjusted, the pointer indicates the level of the top of the weir from the zero position on the calibrated scale.
The equipment is set so that at zero position of the weir, the height just sufficient for initiating gravity flow from the tank is represented. A line E2 permits water to be circulated from the tank at constant head for the experiment. A glass test chamber F (5”OD x36” height) is enclosing a 1/2 ” nominal type copper condenser F1 ( 5/8 “ OD x 0. 040” wall thickness) with a test length of 24” surrounded by a brass expanded metal cylinder F2 positioned in order to avoid undesired thermal convection effects induced between the tube and the glass.
The Research paper on Heat Flow Geothermal Energy Water
Whether the World Population stabilizes at 8 Billion or 10 Billion, both developing and developed nations will call for increasing amounts of energy as they strive to achieve higher standards of living. The oil crises twenty years ago gave rise to a debate about the availability of energy, adequacy of supply and the hunt for alternatives. Today, there is no shortage of energy, the question is how ...
A flint glass condensate receiver G ( cylindrical 6”OD x 8” height) rests on a wooden shelf below and left of the chamber . The condensate receiver receives condensate which collects at the bottom of the test chamber from which it overflows into the receiver. Steam is fed to the system at the steam inlet SI fitted with a valve V-3 to drain any condensate in the line and a valve V-4 to control the flow of steam. Valve V1 further throttles the steam into the test chamber. The pressure and temperature of the steam is metered by means of a pressure and a temperature gauge.
The steam entering the bottom of the test chamber is discharged vertically downward through a U bend into a stainless steel mesh pad which traps any condensate in the incoming steam and de mists the steam and also distributes the rising steam evenly across the test section. Four Teflon coated chromel-alumel thermocouples T/C1, T/C 2, T/C3 and T/C4 connected through a selector switch, measures the inlet and outlet temperatures of the shall side and tube side fluids. Leads of the four thermocouples are connected to a selector switch mounted on the front panel of the apparatus.
Water leaving the heat exchanger is collected at the receiver R and is discharged trough the valve W-3. All the valves S-1 to S3, V1-V-4 and W-1 – W4 incorporated in the unit are shown in Figure 8. 2. Page 4 of 15 Experiment 8 – Free & Forced Convection Convection Heat Transfer. doc FIGURE 8. 2 LAY OUT OF THE FREE AND FORCED CONVECTION UNIT A view of the unit is shown in Figure 8. 3 Page 5 of 15 Experiment 8 – Free & Forced Convection Convection Heat Transfer. doc FIGURE 8. 3 THE EXPERIMENTAL RIG 8. 4. SERVICES AND MATERIALS REQUIRED Water supply.
Power Supply 220V AC Steam Supply 8. 5 PRE EXPERIMENTAL QUESTIONS 1. Identify the following units in the apparatus. (a) Feed Tank (b) Weir height calibrating scale (c) Condensate Receiver (d) Test heat exchanger tube and condenser (e) Drain valves (f) Steam inlet valve (g) Thermocouples and the selector switch 2. Explain the difference between the Natural convection and forced convection 3. Estimate the flow rates of water required to attain the following Reynold Numbers for flow through the heat exchanger tube. 100, 1000, 2000, 5000, 10000, 25000, 30000, 50000
The Term Paper on Heat Pump
Outdoor components of a residential air-source heat pump A heat pump is a machine or device that transfers thermal energy from one location, called the “source,” which is at a lower temperature, to another location called the “sink” or “heat sink”, which is at a higher temperature. Thus, heat pumps moves thermal energy opposite to the direction that it normally ...
Page 6 of 15 Experiment 8 – Free & Forced Convection Convection Heat Transfer. doc 8. 6 PROCEDURE Caution for safety: 1. You must familiarize yourself with the flow paths and apparatus (including valves) before beginning of the experiment. 2. Low pressure steam and water should be used in this experiment. The rig T9054 has been hydraulically tested at 60 psig. The working pressure should be below 35 psig. 3. At the onset of admitting steam to the system, the steam valve should be opened slowly and cautiously in order to detect any possible leaks in the system. . Make sure the steam chest is vented and check the liquid seal plugged before closing the vent while the steam is on. 5. Wear heat resistant gloves as exposed steam lines are hot and could burn. 6. If a steam valve is detected to be unduly tight, never attempt to open the valve by force using a pipe wrench. In such a case, always turn the steam off and allow the system to cool down before force opening the valve. 7. Avoid water spillage on the floor in avoid mishaps due to slippery surfaces.
