Carrier 09RH specifications Thr, Condenser Water Circuiting

Water Circuiting Arrangements — The water cir- cuiting arrangement selected for 5F and 09RH condensers

Determine condenser loading factor by use of following formula:

depends on available condenser water pressure, temperature, quantity and source. Refer to Table 32.

LF =

THR

Refer to the Carrier System Design Manual for specific

SDT – 1.5 line loss – EWT

information and recommendations for refrigerant and water

=

153

piping.

Economics — Selection of a condenser requires balancing of certain economic variables, including:

1.First cost of compressor-condenser combination.

2.Operating costs.

3.Ratio between power costs and water costs.

Where first cost is the most important consideration, the best combination of compressor and condensers has the lowest total equipment cost.

If owning and operating costs are important, combination must be selected on basis of both considerations.

A condenser selection that permits operation of the system at a low condensing temperature, results in the lowest compres- sor motor brake horsepower and consequently, lowest operat- ing cost. A condenser selection that is heavily loaded requires the compressor to operate at a higher condensing temperature and results in higher compressor motor brake horsepower and operating cost.

For a given compressor-condenser combination, selection of a condensing temperature may depend on a ratio between power costs and water costs, on quantity of water available, on condensing temperature required to achieve compressor capacity, or a requirement to remain within allowable loading on a given motor size.

Condenser Performance with Ethylene Gly- col — Increased use of closed circuit cooling towers has led to a corresponding increase in the need for shell and tube con- denser ratings for use with ethylene glycol. When towers are installed outdoors, a brine solution is required for freeze protec- tion during winter operations.

In most outdoor installations, specifications will call for a percentage of concentration of ethylene glycol or other brine solution. If concentration is not specified, it may be the choice of the contractor to determine a percentage of glycol concentra- tion to ensure against freeze-up during winter minimum design ambients.

To perform simplified selection, use Fig. 22 to convert a condenser water rating to a brine rating.

EXAMPLE:

Assume that a building with a year-round cooling load has a cooling requirement of 120 tons during summer design condi- tions. Chilled water design temperatures are 54 F entering to 44 F leaving, and for summer duty, the condenser water is based on 85 F and a 10 degree rise.

From product literature, selected unit will deliver 121 tons at 105.8 F saturated discharge temperature (SDT) and has 153 tons of heat rejection.

(105.8 – 1.5) – 85

= 19.3153 = 7.9

Where: EWT — Entering Water Temperature LF — Loading Factor

THR — Total Heat Rejection

The 85 F value is return water temperature from closed cir- cuit cooler.

Entering condenser rating data at loading factor of 7.9, 300 gpm are required to maintain design condensing tempera- ture. Next, determine the rise by:

Rise = THR x 24

Gpm

= 153 x 24 = 12.2 degrees 300

If a more precise rise is desired, go back and assume a slightly different condensing temperature, recalculate the load- ing factor and rise and repeat the procedure until a final balance is found.

For this example, condenser water pressure drop is approxi- mately 9.4 ft for the design 300 gpm flow rate. Using Fig. 22, flow rate correction can be determined for any glycol concen- tration versus water in shell and tube condensers.

Continuing with example, assume specifications required protection against freeze-up at an ambient of 0° F. (A glycol concentration that provides protection between 10 and 15 de- grees below expected minimum ambient has been the design criteria for many years.)

In a condenser system, the use of proper ethylene glycol brine concentration is important because of the phenomenon that commonly published freeze points are not freeze points but are the point of crystallization where the first crystals begin to form. Actual freezing into a solid occurs at much lower temperatures. For example, freeze point of 20% ethylene glycol is given as +16 F but does not become a solid until it reaches –50 F; 35% ethylene glycol with a freeze point of –6 F does not become solid until it reaches –120 F. Consequently, 20% glycol solution will take care of most domestic applica- tions and 35% brine should satisfy the rest. The lowest con- centration of brine will be the most efficient and result in considerable energy conservation.

Entering Fig. 22 at 0° F crystallization point, necessary concentration of glycol is either 32.5% by weight or 30% by volume. Next, determine glycol flow rate:

THR (tons) x Glycol Factor (GF)

Glycol Flow Rate =

Rise

Table 32 — Condenser Water Circuiting

WATER CIRCUITING	CONDENSER SIZE	CONDENSER	NORMAL USE
ARRANGEMENTS		CHARACTERISTICS
Double Circuit	5F20, 5F30	High Water Quantity
4 Passes	5F40, 5F60		Cooling Tower
		Low Pressure Drop
3 Passes	All 09RH
Single Circuit	5F20, 5F30	Low Water Quantity
8 Passes	5F40, 5F60		City or Well Water
		High Pressure Drop
6 Passes	All 09RH

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