**1. Introduction**

A spiral heat exchanger is assembled by two metallic plates separated by studs. They are welded on the plate surface. The objective is to maintain a constant spacing between plates at the time the plates are rolled up. Thus, the first turn represents one flow section; at this point, the second flow section initiates. Fluids pass in spiral plate heat exchangers by two arrangements, cross-flow and spiral flow, and these configurations are shown in **Figure 1**. Since these patterns were stated, manufacture companies and researchers have proposed more understandings regarding designs, thermal and hydraulic analyses and ways to provide more worth to these heat exchangers.

Spiral plate heat exchangers have important industrial applications; particularly, they are suitable for dirty fluids and viscous fluids. However, most of the correlations and methods explain the single-phase liquid-liquid, and as a consequence, this is not sufficiently to describe heat transfer and hydraulic behaviour, i.e., two-phase flow in spiral heat exchangers liquid–gas and liquid-vapour. Sathiyan et al. [1, 2] presented a study to evaluate a new equation to approximate the Nusselt number of

metal construction characteristics. Thermal and hydraulic model is a key relationship which reduces the calculations to sizing and performs heat exchangers. Commonly, five iterations are needed to reach the balance between pressure drop and heat transfer. Finally, the heat transfer area is determined. The present procedure primarily introduces a hydraulic equation which is a function of pressure drop, the spacing between plates, flow rate and spiral plate length. The correlation is solved iteratively for the length; if the calculated length does not satisfy the pressure drop design, the spacing plate could adjust to maximise the use of permissible pressure drop.

*Designing Spiral Plate Heat Exchangers to Extend Its Service and Enhance the Thermal…*

The hydraulic equations were presented by Minton [16]. These correlations are a

[16]. Eq. 2 (**Table 1**) has the same approach; however, the pressure drop is negligible because the fluid flows across the plate width, and value close to zero represents minor influence even by installing the studs [16]. Calculating the Reynolds number and the critical Reynolds number values is possible to select the correct equation to describe the hydraulic operation of the spiral plate heat exchangers. The equations are developed for the three flow regimes: laminar, transition and turbulent. The

The thermal model equations were introduced by Minton, although Sander [17]

Eq. (3) describes the heat transfer coefficient for a liquid fluid flowing by the spiral side. Similarly, Minton presented 11 mechanisms to determine the heat transfer coefficient as a function of flow configuration, type of service (condensing and heating) and a vertical nucleate boiling. Eq. (4) is for gas fluid where the Reynolds number is higher than 10,000. Even when this number is above critical Reynolds number, gases have low heat capacity, and they have poor heat transfer

**Flow configuration Empirical pressure drop correlation**

**Flow configuration Empirical heat transfer coefficient**

*<sup>s</sup> <sup>F</sup> dsH* h i<sup>2</sup> <sup>1</sup>*:*3*μ*1*=*<sup>3</sup> ð Þ *ds*þ0*:*<sup>125</sup> *<sup>H</sup> F*

(3) *<sup>h</sup>* <sup>¼</sup> <sup>1</sup> <sup>þ</sup> <sup>3</sup>*:*<sup>54</sup> *De*

� �<sup>1</sup>*:*<sup>8</sup> 0*:*0115*μ*<sup>0</sup>*:*<sup>2</sup> *<sup>H</sup>*

**correlation**

(4) *<sup>h</sup>* <sup>¼</sup> <sup>0</sup>*:*0144*cG*<sup>0</sup>*:*<sup>8</sup>*D*�0*:*<sup>2</sup> *<sup>e</sup>*

*DH* � �0*:*023*cGRe*�0*:*<sup>2</sup>

*sds* 2 *F L*

For spiral flow without phase change Re>Rec (1) *<sup>Δ</sup><sup>P</sup>* <sup>¼</sup> <sup>0</sup>*:*<sup>001</sup> *<sup>L</sup>*

For axial flow without phase change Re>10*;* <sup>000</sup> (2) *<sup>Δ</sup><sup>P</sup>* <sup>¼</sup> <sup>4</sup>*x*10�<sup>5</sup>

For spiral flow without phase change (liquid fluid)

For axial flow without phase change (gas fluid)

*Correlations for heat transfer coefficient [16].*

, a stud is installed

� �<sup>1</sup>*=*<sup>3</sup> <sup>þ</sup> <sup>1</sup>*:*<sup>5</sup> <sup>þ</sup> <sup>16</sup>

� � <sup>þ</sup> <sup>1</sup> <sup>þ</sup> <sup>0</sup>*:*03*<sup>H</sup>* h i

h i

*ds*

*L*

*Pr*�2*=*<sup>3</sup>

function of a flow along the spiral channel which is separated by studs to give support to the plates. Factor 1.5 in Eq. 1 (**Table 1**) supposes 17 studs per square foot.

Every stud has a diameter of 0.3125, and, then, in every 0.118 in<sup>2</sup>

hydraulic correlations used in this study are presented in **Table 1**.

**2.1 Hydraulic equations**

*DOI: http://dx.doi.org/10.5772/intechopen.85345*

**2.2 Thermal equations**

coefficient values (**Table 2**).

*Correlations for pressure drop [16].*

**Table 1.**

*Re*>*Rec*

**Table 2.**

**209**

Re > 10,000

proposed the heat transfer correlation earlier.

**Figure 1.** *Cross-flow and spiral flow arrangement.*

an immiscible mixture using a countercurrent spiral heat exchanger for two-phase flow. The new correlation was based on the experimental data, and the results were agreement with the theoretical correlation. Khorshidi and Heidari [3] fabricated a spiral heat exchanger geometry to study the performance, the examination showed that spiral heat exchanger is an excellent option to transfer heat especially from fouling fluids and also a computational fluid dynamic was presented to determine a previous design. Ramachandran et al. [4] determined the heat transfer behaviour for a system of two fluids by implementing a countercurrent spiral plate heat exchanger; the data were obtained from varying mass fraction inlets and demonstrated efficient results between the experiment and the correlation. Maruyama et al. [5] measured the thermal effectiveness of a cross-flow spiral plate heat exchanger; the aim was to convert radiation energy from a combustion chamber. Wang [6] analysed the thermal performance of a spiral plate heat exchanger used as an adsorber in a refrigeration process, the flows were configured to follow a spiral trajectory and the spiral exchanger resulted appropriated for a refrigeration system. Bahiraei et al. [7, 8] presented a study to evaluate the thermal and hydraulic performance of a spiral plate heat exchanger under a turbulent flow of a nanofluid. The experimental procedure was to determine the effects due to the spiral geometry varying the flow rate to define the optimal operational conditions.

The thermal and hydraulic concept is an innovative tool to achieve designs for heat exchangers and applies to all types of heat exchangers. Previously, researches have been using this procedure [9, 10]. Compact and conventional exchangers are employed to develop two duties heating and cooling. Nevertheless, they behave differently from each other due to their geometrical configuration, effectiveness, outlet temperature, pressure drop and heat transfer area [11–15].

The current study is organised to describe four main purposes: 1. To present two design methods by a thermal and hydraulic procedure. The first design is for a cooler using a cross-flow arrangement (liquid-gas) without phase change, to evaluate if a spiral plate heat exchanger can take part as a radiator of the cooling system car. The second approach is to size a vertical spiral heat exchanger condenser for a cryogenic operation. 2. To extend the operational activities of spiral plate heat exchangers. 3. To improve the spiral thermal and hydraulic performance by modifying the spacing plate. 4. A numeric analysis applying computational fluid dynamics to validate the method.
