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. The airside system is considered to be the same performance as for the chilled-water system. face velocity through the coil and ensuring proper drainage are essential to prevent moisture carryover. 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). Second, the drain pan in the bottom of the unit for a 96” high coil would be enormous. 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: Active coil face velocity can vary from 100 to 67% of design (440 to 295 fpm/ 2.2 to 1.5 m/s). At part load, only a portion of the coil face remains active. - 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. minimum of 6 inches 5 E N 14 06 C 24.00 x 144.00 . S. Tredinnick, G. Phetteplace, in Advanced District Heating and Cooling (DHC) Systems, 2016. 3.3 Forced-Circulation Air Coil. To simplify the equation, the new dependent variable is introduced: www.intechopen.com DX CALCULATION. 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. •Fraction circuiting (0.25, 0.33, 0.5, 0.75) –Multiple tubes are circuited together to increase tube velocity 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. of face area per hour under peak sensible and peak dew point design conditions , considering both latent load and coil face velocity. Quantity of standard air to be cooled. The face velocity of air through the coil should range from 400 to 600 feet per minute. Selecting a maximum face velocity will determine a minimum face size but the length to height ratio will have effect on cost. DX condenser coils are available with multiple rows, up to 22 fins per inch, and can be configured with interlaced or face split circuitry. 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. 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. Figure 4A. The number of fins per inch is determined by the allowable air friction loss. 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. Face Pitch is the centerline distance between two consecutive tubes in the coil face… Under 350 should be … °C) m =outside diameter, (m) 5. 3 evaporator Coil types ... (Figure 2) is used for face control. d. coil face velocity >550 FPM . Moving to 300-400 FPM velocity adds a small % first cost but saves big in supply fan HP over life of unit. Filter Face Air Velocity (FPM) 492 Maximum Initial Resistance (Inches W.G.) Face Pitch. Coils operating with all or high fresh air content are particularly vulnerable. 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 Within limits, the … All DX evaporator coils and heat pump condenser coils include rifled tube enhancements and refrigerant distributors that ensure proper refrigerant distribution into the coil. And, it would be practically “raining” off the top of a coil 96” high. It is a balance between the desired capacity and the resultant 20 When I have had to do this, I always work with a coil company. Description The filter media shall be bonded to a sturdy water-resistant coated beverage board filter frame to fit industry standard size filter racks. 3.3.1 Forced-Circulation Air-Cooling Coil. 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 Super heat %Ref DP/TD. This temperature does not include superheat. A type of Coil which has damper(s) A heat exchanger, with or without extended surfaces, through which 1.0 Minimum MERV Rating 8 B. Local high velocities and moisture tracking causing spillage are best avoided by downstream drainage. Anything higher and you are asking for complications. Air velocity for chilled water or DX coils should never be higher than 550 feet/min. scfm fpm face vel. 0.40 Minimum Rated Final Resistance (Inches W.G.) Figure 4B. 500 10,000 1/2 20.25 10,000 1. Entering air wb and db temperature. 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. 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. 8.6.1 Deeper coils for higher ΔT. Glycol % has a drastic negative effect on transfer properties making GPM, coil and piping sizing go up. 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). This is termed scfm b. 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. The other consequence of dropping airflow is lower overall sensible capacity and therefore a drop in EER and SEER rating. VIEW EXISTING RUNS UPLOAD TEST CSV FILE. Certified Characteristics. to obtain face velocity in FPM. Face Control is the simplest form of capacity control. e. coil is located immediately upstream of bottom discharge in … 1.2.1.2 Forced-Circulation Air-Heating Coil. Design parameters used are: coil face velocity of 2.0 m/s, air inlet relative humidity of 90%, temperature 30 °C, refrigerant enthalpy 351 . AAON DX coils are designed A coil for use in an air stream whose circulation is caused by a difference in pressure produced by a fan or blower. The value of 500 fpm (2.5 m/s) is very commonly used for coil sizing and it works very 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. Traditional Face Split. I provide the specifications: any required dimensions, cooling capacity or heat of rejection, face area, air velocity, etc. c. spiral fins in lieu of plate fin type coils . Type EF coils are normally furnished with two distributors and two suction connections offer-ing 50% capacity reduction capabilities. A face velocity of 500 feet per minute is generally accepted as the most desirable. 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 To select a coil, the following information must be determined from system requiremenst: a. Our Daikin E-F (energy-efficient) fins save energy by reducing air pressure drop as much as 33% and lowering fan brake horsepower requirements. Add a new Section 5.12 to specify requirements for finned-tube coils in the air distribution system. Positive coil freeze protection must be used in … 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. DX Coil capacity is inversely proportional to evaporating temperature. If space allows, making coil section larger to reduce velocity. Actual face velocity = = 494 fpm. Face velocity, fin spacing, finned height and latent cooling rate (SHR) are all contributory factors and differing combinations will change these affects. This face velocity shall be based on the actual coil face area sans any safing around the coil. 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. DOWNLOAD CSV FILE. The amount of superheat at the exit of the DX coil has been factory set at 10 °F for calculation purposes. Number of circuits Out. c. leaving air wb and db temperature required. Air velocity: For a given cfm of air, a reduction in coil face area increases coil face velocity over the coil tubes. 5. Type II – Pleated panel filters 1. casing and headers (a minimum of 10 inches be-yond the leaving face of the coil). 1.2.1.3 Integral Face and Bypass Coil. installing open coil duct heaters into velocities over 1200 feet per minute contact your local INDEECO representative. Ft) Air pressure drop (inches H2O) Fins per inch. The coil company engineers come back with choices available to achieve the design: coil depth, fin spacing, number of passes, etc. c. Air flow is greater than 25% but less than 50%, two dampers and solenoid valves will open. 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. Active coil face velocity can vary from 100 to 50% of design (440 to 220 fpm 2.2 to 1.1 m/s). Coil choices include water cooling, water heating, steam, booster, evaporator and condenser. The maximum face velocity for cooling coils in both custom and emi-customs units shall be limited to 450 FPM. Governing equations and methodology The sizing of cooling coil requires solving the two energy equations of the air-side and Coil Face Area (Sq. A long narrow coil has less tubes, welding and manifold than a more square coil making it cheaper to manufacture. Face velocity (Feet/Min) Pressure drop (ft H2O) Refrigerant flow rate (lbs/hr) Number of circuits In. b. coil fin height >36”; tall coils will tend to carryover at lower velocities . Always question unit design and operation if they request 40% 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. Our Daikin Hi-F (high-efficiency) fins maximize heat transfer with less fins to lower your initial cost. Face velocity is restricted to 500 fpm (2.5 m/s) to avoid carryover of condensate from the coil. Allows, making coil Section larger to reduce velocity maximize heat transfer with less fins to your. ) pressure drop ( inches H2O ) fins per inch Advanced District Heating and cooling ( DHC ) Systems 2016! 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