3 evaporator Coil types ... (Figure 2) is used for face control. Under 350 should be … Quantity of standard air to be cooled. Filter Face Air Velocity (FPM) 492 Maximum Initial Resistance (Inches W.G.) Coils operating with all or high fresh air content are particularly vulnerable. face velocity through the coil and ensuring proper drainage are essential to prevent moisture carryover. WATER VELOCITY FEET PER SECOND (FPS) WATER VELOCITY FPS* = GPM × Factor ÷ Number of Tubes Fed Tube Diameter Factor 5/8 “ OD 1.085 1/2” OD 1.704 3/8” OD 3.050 **As Water Velocity increases, the capacity of a coil increases, but so does the water resistance. Our Daikin Hi-F (high-efficiency) fins maximize heat transfer with less fins to lower your initial cost. Selecting a maximum face velocity will determine a minimum face size but the length to height ratio will have effect on cost. to obtain face velocity in FPM. Coil Face Area (Sq. The maximum face velocity for cooling coils in both custom and emi-customs units shall be limited to 450 FPM. The amount of superheat at the exit of the DX coil has been factory set at 10 °F for calculation purposes. Second, the drain pan in the bottom of the unit for a 96” high coil would be enormous. 3.3.1 Forced-Circulation Air-Cooling Coil. Coil TD increases as indicated by the colder coil in relationship to the return air; We all know that if you have far too little airflow a system can freeze up when the coil temperature drops below 32°F. Local high velocities and moisture tracking causing spillage are best avoided by downstream drainage. Air velocity: For a given cfm of air, a reduction in coil face area increases coil face velocity over the coil tubes. of face area per hour under peak sensible and peak dew point design conditions , considering both latent load and coil face velocity. Face Pitch. Actual face velocity = = 494 fpm. This face velocity shall be based on the actual coil face area sans any safing around the coil. Figure 4B. Suction pressure remains low in the active circuit, thus providing a lower fin temperature and leaving air temperature in the active portion of the face. •Fraction circuiting (0.25, 0.33, 0.5, 0.75) –Multiple tubes are circuited together to increase tube velocity e. coil is located immediately upstream of bottom discharge in … This is termed scfm b. The value of 500 fpm (2.5 m/s) is very commonly used for coil sizing and it works very Ft) Air pressure drop (inches H2O) Fins per inch. Description The filter media shall be bonded to a sturdy water-resistant coated beverage board filter frame to fit industry standard size filter racks. c. spiral fins in lieu of plate fin type coils . When I have had to do this, I always work with a coil company. Traditional Face Split. Design parameters used are: coil face velocity of 2.0 m/s, air inlet relative humidity of 90%, temperature 30 °C, refrigerant enthalpy 351 . The airside system is considered to be the same performance as for the chilled-water system. - arrangement of coil in relationship to the direction of the airflow - minimum and maximum number of rows - minimum and maximum number of tubes per row - minimum and maximum finned length. Coil choices include water cooling, water heating, steam, booster, evaporator and condenser. 8.6.1 Deeper coils for higher ΔT. The other consequence of dropping airflow is lower overall sensible capacity and therefore a drop in EER and SEER rating. c. Air flow is greater than 25% but less than 50%, two dampers and solenoid valves will open. Certified Characteristics. to the compressor, a minimum velocity must be maintained in the piping so that sufficient oil is returned to the compressor sump at full and part load conditions. S. Tredinnick, G. Phetteplace, in Advanced District Heating and Cooling (DHC) Systems, 2016. Glycol % has a drastic negative effect on transfer properties making GPM, coil and piping sizing go up. Positive coil freeze protection must be used in … Entering air wb and db temperature. d. coil face velocity >550 FPM . Face velocity, fin spacing, finned height and latent cooling rate (SHR) are all contributory factors and differing combinations will change these affects. The actual DX coil furnished for the system was 8 row, 10 fpi, with a face velocity of 440 fpm (2.24 m/s), so it is very near the pressure drop of the coil required for the chilled-water system: DOWNLOAD CSV FILE. A face velocity of 500 feet per minute is generally accepted as the most desirable. In the direct expansion or DX types of air central conditioning plants the air used for cooling space is directly chilled by the refrigerant in the cooling coil of the air handling unit. It is a balance between the desired capacity and the resultant 20 casing and headers (a minimum of 10 inches be-yond the leaving face of the coil). And, it would be practically “raining” off the top of a coil 96” high. VIEW EXISTING RUNS UPLOAD TEST CSV FILE. To simplify the equation, the new dependent variable is introduced: www.intechopen.com All DX evaporator coils and heat pump condenser coils include rifled tube enhancements and refrigerant distributors that ensure proper refrigerant distribution into the coil. Governing equations and methodology The sizing of cooling coil requires solving the two energy equations of the air-side and Face velocity is restricted to 500 fpm (2.5 m/s) to avoid carryover of condensate from the coil. A good rule of thumb is a minimum of: • 500 feet per minute (fpm) or 2.54 meters per second (mps) for horizontal suction and hot gas lines AAON DX coils are designed DX condenser coils are available with multiple rows, up to 22 fins per inch, and can be configured with interlaced or face split circuitry. Moving to 300-400 FPM velocity adds a small % first cost but saves big in supply fan HP over life of unit. 372 Heat Exchangers Basics Design Applications Where, k g l = minimum free-flow air area, (m 2) _ = mass flow rate of air through the cooling coil, (kg/s) J _ =dynamic viscosity of air (kg/m.s) _ =thermal conductivity of air (W/m. Type II – Pleated panel filters 1. k A dx hPdx T T dx dx (5) and 2, 2,, 1 kx ()0 S kx f kx dT dT hPdA T T dx A dxdxkA (6) or 2, 2 2 (ln ) kx ()0 S dT dTdA mT T dx dx dx (7) where 2 f kx, hP m kA (8) Both P and A kx, are the function of x or a variable cross section. 1.0 Minimum MERV Rating 8 B. The 2.5 m/s rule for sizing cooling coils is adequate to keep water droplets from leaving the outer edge of the discharge side of the coil (carryover). minimum of 6 inches 5 E N 14 06 C 24.00 x 144.00 . A type of Coil which has damper(s) The finned height and finned length (face area) of the coil must be chosen to give an acceptable face velocity (volume flow rate divided by face area). 500 10,000 1/2 20.25 10,000 1. A heat exchanger, with or without extended surfaces, through which Air velocity for chilled water or DX coils should never be higher than 550 feet/min. Face velocity (Feet/Min) Pressure drop (ft H2O) Refrigerant flow rate (lbs/hr) Number of circuits In. At part load, only a portion of the coil face remains active. Number of circuits Out. The direct expansion or the DX type of central air conditioning system is usually used for cooling the small buildings or the rooms on the single floor. Add a new Section 5.12 to specify requirements for finned-tube coils in the air distribution system. DX Coil capacity is inversely proportional to evaporating temperature. 1.2.1.2 Forced-Circulation Air-Heating Coil. Type EF coils are normally furnished with two distributors and two suction connections offer-ing 50% capacity reduction capabilities. Super heat %Ref DP/TD. The drain pan must be elevated to provide free drainage of con-densate and to provide ample space for installation of a trap in the drain line, to overcome pressure in the coil casing. 5. Typical Dry Coil Pressure Drop in inches of H2O at 500 fpm Rows 90 fins/ft 120 fins/ft 150 fins/ft 168 fins/ft If space allows, making coil section larger to reduce velocity. Face Control is the simplest form of capacity control. Active coil face velocity can vary from 100 to 67% of design (440 to 295 fpm/ 2.2 to 1.5 m/s). installing open coil duct heaters into velocities over 1200 feet per minute contact your local INDEECO representative. I could turn the heat on and get delta T and use-btu output x 1.08 /delta T to obtain CFM, then use CFM /area of coil in sqft. Always question unit design and operation if they request 40% Figure 4A. 0.40 Minimum Rated Final Resistance (Inches W.G.) Within limits, the … Anything higher and you are asking for complications. The coil company engineers come back with choices available to achieve the design: coil depth, fin spacing, number of passes, etc. 1.2.1.3 Integral Face and Bypass Coil. A coil for use in an air stream whose circulation is caused by a difference in pressure produced by a fan or blower. To select a coil, the following information must be determined from system requiremenst: a. Face Pitch is the centerline distance between two consecutive tubes in the coil face… Our Daikin E-F (energy-efficient) fins save energy by reducing air pressure drop as much as 33% and lowering fan brake horsepower requirements. Active coil face velocity can vary from 100 to 50% of design (440 to 220 fpm 2.2 to 1.1 m/s). b. coil fin height >36”; tall coils will tend to carryover at lower velocities . The face velocity of air through the coil should range from 400 to 600 feet per minute. This temperature does not include superheat. DX CALCULATION. A heat exchanger, with or without extended surfaces, through which either hot water, hot aqueous ethylene or propylene glycol solutions, or steam is circulated for the purpose of sensible heating of a forced-circulation air stream. scfm fpm face vel. 3.3 Forced-Circulation Air Coil. Coil face dimensions In designing an evaporator for a particular requirement, the factor which most influences its dimensions is the volume flow rate of air to be cooled. c. leaving air wb and db temperature required. A long narrow coil has less tubes, welding and manifold than a more square coil making it cheaper to manufacture. The cooling coil’s air face velocity shall be sized for a nominal air face velocity not to exceed 2.0 m/s (400 fpm) for the present design conditions and 2.5 m/s (480 fpm) for the future growth capacity. I provide the specifications: any required dimensions, cooling capacity or heat of rejection, face area, air velocity, etc. desired tube velocity •Number of tubes in coil face is a function of coil height •Tube sizes (3/8”, 1/2”, 5/8”) •Circuiting Options •Full or 1 –All tubes in face have equal full. Coil Face velocity (fpm) 4 GENERAL 1 To calculate unit dimension, each "Module" = 342mm Eg YSM / YBM 40x60 Height : (4x342 + 58 +100)mm Width : (6x342 + 58)mm Eg YDM / YCBM 40x60 Height : (4x342 + 108 + 100)mm Width : (6x342 + 108)mm NOTE : 100mm unit base to be included when calculate for unit height dimension The number of fins per inch is determined by the allowable air friction loss. °C) m =outside diameter, (m) 5.