The pressure drop caused by piping
valves, fittings and other singularities is not the same in turbulent
flow and in laminar flow. Turbulent flow have been extensively
studied, thus the coefficient are available for many equipment but it
is less the case in laminar flow. This page is giving some references
from literature **for laminar flow.** Please consult those
references for more details.

## 2. Pressure drop calculation

K coefficient can reasonably be used until Re=500, below, specific
coefficients should be used.

#### 2.1 Kittredge and Rowley

The data of Kittredge and Rowley are reported in many books. They
have tabulated the frictional loss coefficients for different
fittings and valves and different Reynolds. If the flow is found to
be laminar they should be used in pressure calculation instead of
the coefficients calculated for turbulent flow

**Table 1 : K coefficient for
calculation of pressure drop through valves and fittings in
laminar flow according to Kittredge and Rowley**

#### 2.2 Hooper

As an alternative, the method of Hopper can be used. As most of the
data obtained in laminar flow, results are approximate.

The frictional loss coefficient can be calculated from the value in
turbulent flow and coefficients to account for laminar flow :

**Equation 1 : Hooper approximation
for calculation of pressure drop coefficients of valves and
fittings in laminar flow**

With :

- K_{1} = pressure drop coefficient for Re=1

- K_{t} = coefficient in turbulent flow

If unknown, K_{t} can be calculated with the following
formula where K∞ is the coefficient in turbulent flow for a very
large diameter

**Equation 2 : Calculation of
turbulent frictional loss coefficient for Hooper method**

Coefficient K_{1} can be
calculated thanks to the following table.

**Table 2 : K1 coefficient for
calculation of pressure drop through valves and fittings in
laminar flow with the approximation of Hooper**

Source

Mecanique et Rheologie des Fluides en
Genie Chimique, Midoux, Tec et Docs, 1993, pages 348

Perry's Chemical Engineers Handbook, Perry, McGraw Hill, 2008, page
6-18